their radiological features suggest malignant neoplasms , whereas they are not  ct and mr imaging are the most used tools in their evaluation inflammatory myofibroblastic tumours ( imts ) constitute a rare group of neoplasms composed of a mixture of spindle - shaped myofibroblasts or fibroblasts and a variable amount of inflammatory cells ( eosinophils , plasma cells and lymphocytes ) . many different terms have been used to refer to these tumours : plasma cell granuloma , inflammatory myofibrohistiocytic proliferation , fibroxanthoma , xanthogranuloma . the most frequently affected organs are lung and orbit , but they have been described in nearly every organ . different aetiologies have been proposed for imt , being different chronic infections , autoimmune diseases and trauma the most accepted . specific inflammatory diseases , such as igg4 disease , have also been recently associated [ 4 , 5 ] . an aggressive behaviour with metastases has been described [ 3 , 6 , 7 ] . clinical presentation of imts depends on the organ in which they arise , but they frequently associate general inflammatory symptoms as fever or malaise . radiological appearance of imts is unspecific and they are often misdiagnosed as malignant neoplasms . many of them are incidentally discovered when an imaging technique ( computed tomography [ ct ] , ultrasonography [ us ] or magnetic resonance imaging [ mri ] ) is performed for any other reason . their most common radiological presentation is as solid , irregular , well - defined masses . immunohistochemical studies of t- and b - cell subpopulations , cd34 , cd117 , s-100 and c - kit may be helpful in distinguishing imts from other soft - tissue neoplasms [ 8 , 9 ] . at the molecular level , approximately half of imts contain a clonal cytogenetic aberration that activates the anaplastic lymphoma kinase ( alk- ) . positive immunohistochemical staining of alk is in approximately 40100  % of imts , depending on the anatomical sites where they arise [ 810 ] . furthermore , alk expression could be a prognostic factor of aggressiveness for imt . according to an update based on the new world health organisation ( who ) classification , imts are considered as neoplasms which may recur or metastasise in as many as 5  % of cases . the objective of this pictorial review is to present the most important characteristics of imts arising in different locations of the body with their histological correlation . , these tumours can appear as hypoechoic or hyperechoic masses with ill - defined or well - circumscribed edges and a variable doppler appearance with increased vascularity . us is usually the first imaging technique when imts appear in specific locations , such as testicles or neck . in other locations on contrast - enhanced ct , imts can appear as homogeneous or heterogeneous lesions , with variable enhancement on delayed acquisitions due to the presence of fibrosis . these findings are also present on gadolinium contrast - enhanced mri . on t1-weighted and t2-weighted sequences , imts usually show low signal intensity reflecting also the presence of fibrotic tissue ( table  1).table 1symptoms , radiological findings and differential diagnosis of the main imts of the bodysymptomsimaging findingsdifferential diagnosisorbitpain , redness , oedema , proptosis , ptosis , oculomotor deficits , diplopia , swelling , mass - effectsolid and heterogeneous enhancing . associated retrobulbar fat or oedemagranulomatous diseases , primary infection , sarcoid , sjgren disease , primary and secondary tumours of the orbit , lymphoma and connective tissue diseaseslungcough , chest pain , dyspnea , haemoptysis , fever , malaise and weight loss.solitary , well - circumscribed , peripheral , predominance for the lower lobes , unusual calcifications . low intensity on t2-weighted imagesmalignant lung masses : primary bronchogenic carcinomascrotumlump in the scrotumsolid and heterogeneous masses with internal vascularity on us . small calcifications can be associatedscrotum primary neoplasmhepaticunspecific , depending on the sizeheterogeneous or peripheral enhancement during the arterial phase . or homogeneous enhancement during the arterial phase and washout during the delayed phase on ct . t1 hypointense and t2 hyperintense with heterogeneous enhancementhccsplenicleft upper quadrant or epigastric painlow - density pattern . low - intensity lesion in the early phase after gadolinium injection and high - intensity in the delayed phasesplenic haemangioma and other primary splenic neoplasms as lymphoma or splenic angiosarcomagrastrointestinal tract and mesenteryabdominal pain , intestinal obstruction , dysphagia , anaemiahypodense , heterogeneous , well - delimitedgist , inflammatory fibroid polyp , smooth muscle neoplasm , peripheral nerve sheath tumour , solitary fibrous tumour , fibromatosis , the follicular dendritic cell sarcoma , lymphoma and adenocarcinomamusculoskeletalpain , oedemanon - homogeneous , solidmalignant lesions : rabdomyosarcoma symptoms , radiological findings and differential diagnosis of the main imts of the body imts have been reported in various sites in the head and neck such as bucal space , maxillary sinus , nasal cavity , parotid gland , nasopharynx and larynx ( fig . 1pathology : imt in the left supraglottic space ( arrow ) with paraglottic space involvement indicated by replacement of the paraglottic fat with soft tissue . a axial reformation of contrast - enhanced neck ct . a solid , well - defined , normal tissue was present in the peripheral zone ( * ) pathology : imt in the left supraglottic space ( arrow ) with paraglottic space involvement indicated by replacement of the paraglottic fat with soft tissue . a axial reformation of contrast - enhanced neck ct . a solid , well - defined , little - enhancing nodule in the supraglottic larynx was observed ( yellow arrow ) . b microscopic study obtained after surgical removal of the lesion . the sample showed proliferation of fusiform cells mixed with macrophages and giant multinucleated cells . normal tissue was present in the peripheral zone ( * ) however , the orbit is the most common location of imts . they account for approximately 10  % of orbital masses , being the third most common cause of orbital masses . their aetiology is unknown , but they have been associated with inmunological disorders , different infections and history of trauma . recently , they have been strongly associated with the igg4-related sclerosing systemic inflammatory disease   and with chronic infection by epstein - barr virus . the clinical presentation and symptoms may vary with the location , extension and aggressiveness of the tumour . patients with imts of the orbit can present local symptoms as pain , redness , oedema , proptosis , ptosis , oculomotor deficits , diplopia , lid swelling or mass - effect and systemic symptoms due to the general inflammatory disorders they are frequently associated with . mri is superior to ct in the evaluation of inflammation of the nerves and muscles . they usually appear as solid and heterogeneous enhancing masses , which can affect retro bulbar fat , cause bone destruction , and present intracranial extension . when they show low intensity on t2-weighted images prominent , fibrotic composition is present ( fig . a , b axial and coronal mr reformations of the same patient on t2-weighted sequences showed a well - delimited , hyperintense intraorbital mass , in the intraconal compartment , in the medial aspect . c , d t1-weighted images demonstrated a hypointense , homogeneous , well - delimited mass with peripheral enhancement after gadolinium injection . f microscopic sample obtained after surgery demonstrated an epithelial tumour composed of fusiform cells mixed with an extensive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . in the peripheral of the sample a , b axial and coronal mr reformations of the same patient on t2-weighted sequences showed a well - delimited , hyperintense intraorbital mass , in the intraconal compartment , in the medial aspect . c , d t1-weighted images demonstrated a hypointense , homogeneous , well - delimited mass with peripheral enhancement after gadolinium injection . f microscopic sample obtained after surgery demonstrated an epithelial tumour composed of fusiform cells mixed with an extensive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . in the peripheral of the sample striated muscle cells were also observed pathologically , imts of the head and neck consist of many fibroblastic cells , fibroblastic cells and inflammatory cells , which include plasma cells and eosinophils . the differential diagnosis includes granulomatous diseases , primary infection , sarcoid , sjgren disease , primary and secondary tumours of the orbit , lymphoma and connective tissue diseases . the administration of corticosteroids an inmunosupresors usually leads to a decrease of size of the mass but also radiotherapy or surgery may be indicated . they account for around the 50  % of benign pulmonary masses in children , representing only about 0.7  % of all tumours of the lung in general population . as in other organs sometimes , imts are also related with antecedents of lung surgery and they can arise in surgical lung scars . common clinical characteristics include unspecific respiratory symptoms , such as cough , chest pain , dyspnea , haemoptysis and unspecific inflammatory symptoms as fever , malaise and weight loss . they usually appear as solitary , well - circumscribed peripheral lung masses , with predominance for the lower lobes   ( fig . on ct with intravenous contrast , they present a variable heterogeneous or homogeneous degree of enhancement pattern [ 3 , 21 ] . it has been described an aggressive behaviour with invasion of the adjacent structures . on mri because of their similar radiological appearance to malignant lung masses , biopsy is necessary to obtain the diagnosis.fig . a 55-year - old man with a cough and haemoptysis.a axial reformation of non - contrast ct with mediastinum window . two solid , ill - defined nodules in right lower lobe are observed ( yellow arrows ) . b axial reformations with lung window of the same patient where the lung nodules are shown ( white arrows ) . c partial lobectomy of the right lower lobe specimen . note the presence of the nodules ( * ) . d microscopic study of the resected lung sample where fusiform cells with an associated inflammatory infiltrate of lymphocytes , plasmatic cells and histiocytes was found pathology : imt of the lung . a 55-year - old man with a cough and haemoptysis.a axial reformation of non - contrast ct with mediastinum window . two solid , ill - defined nodules in right lower lobe are observed ( yellow arrows ) . b axial reformations with lung window of the same patient where the lung nodules are shown ( white arrows ) . c partial lobectomy of the right lower lobe specimen . note the presence of the nodules ( * ) . d microscopic study of the resected lung sample where fusiform cells with an associated inflammatory infiltrate of lymphocytes , plasmatic cells and histiocytes was found the treatment of choice of lung imts is surgery to exclude malignancy and to achieve the cure . although spontaneous regression may occur , local expansion may cause significant morbidity and occasional death . the prognosis after complete surgical resection is excellent , with a low rate of recurrence . in these cases , alternative treatments ( radiotherapy , corticoids or chemotherapy ) to surgery could be also used . only a few cases of imts in the spermatic cord have been reported . the most common presentation of epididymal ( fig .  4 ) and paratesticular imts is a lump in the scrotum.fig . 4pathology : imt of the epididymus . a 40-year - old man with a lump in the scrotum . a a hypoechoic a diffuse infiltrate composed of fibroblastic and fusiform cells mixed with inflammatory cells ( mainly lymphocytes and macrophages ) was observed pathology : imt of the epididymus . a 40-year - old man with a lump in the scrotum . a a hypoechoic , well - delimited epididymal lesion in the right scrotum was detected . a diffuse infiltrate composed of fibroblastic and fusiform cells mixed with inflammatory cells ( mainly lymphocytes and macrophages ) was observed in the evaluation of scrotal masses , us is the most accurate imaging technique , helping to distinguish intratesticular from extratesticular lesions and solid from cystic lesions . on ct , they appear as well - defined , hypodense masses with little enhancement after intravenous contrast injection . in some cases , a 34-year - old man with no relevant medical history came to our hospital with a lump in the scrotum . a us showed an isoechoic , solid , paratesticular nodule with fine calcifications ( yellow arrow ) . b axial reformation of contrast - enhanced ct on portal phase demonstrated a well - delimited , heterogeneous , little - enhancing mass in the right scrotum . d microscopic study of the lesion demonstrated a well - delimited lesion constituted of fibroblasts , lymphocytes and plasmatic cells with associated lymphoid follicle . a 34-year - old man with no relevant medical history came to our hospital with a lump in the scrotum . a us showed an isoechoic , solid , paratesticular nodule with fine calcifications ( yellow arrow ) . b axial reformation of contrast - enhanced ct on portal phase demonstrated a well - delimited , heterogeneous , little - enhancing mass in the right scrotum . d microscopic study of the lesion demonstrated a well - delimited lesion constituted of fibroblasts , lymphocytes and plasmatic cells with associated lymphoid follicle . there was no evidence of adjacent testicle invasion surgical resection without orchiectomy is the ideal treatment , but in some cases the testicle must be removed due to the size of the mass or when the mass is attached to the testis . imts of the penis are extremely rare . to our knowledge , no imts at this location have been reported . on ct , this tumour appeared as a well - defined , little - enhancing and non - aggressive mass surrounding the penile urethra and the corpora cavernosa with no evidence of invasion of them.fig . a 46-year - old man with a mass in the penis came to our hospital . he related more than 6 years of slow growth of the mass with no suspicious associated symptoms . c , d axial and coronal reformations of enhanced - ct after the injection of intravenous contrast on portal phase . macroscopic view showed an heterogeneous aspect due to the mixture of tissues ( solid tumour , lipoid component and areas of haemorrhage ) . f microscopic study confirmed a mesenchymal tumour composed of fusiform cells , some of them multinucleated , with round or elongate nucleus . a 46-year - old man with a mass in the penis came to our hospital . he related more than 6 years of slow growth of the mass with no suspicious associated symptoms . c , d axial and coronal reformations of enhanced - ct after the injection of intravenous contrast on portal phase . macroscopic view showed an heterogeneous aspect due to the mixture of tissues ( solid tumour , lipoid component and areas of haemorrhage ) . f microscopic study confirmed a mesenchymal tumour composed of fusiform cells , some of them multinucleated , with round or elongate nucleus . no mitotic figures were observed surgical treatment was performed due to the size and non - conclusive radiological features of the tumour . hepatic imts constitute an extremely rare group of hepatic tumours , accounting only for the 0.7  % of all the hepatic lesions . they have been associated with autoimmune diseases , immunological disorders and viral infections , such as igg4 disease , sclerosing cholangitis , crohns disease , hepatic viral infections   and epstein - barr virus . symptoms of hepatic imts depend on their size . on contrast - enhanced ct , they usually show heterogeneous or peripheral enhancement during the arterial phase . despite this , some of them present homogeneous enhancement during the arterial phase and washout during the delayed phase , which can lead to misdiagnosing them as hepatocarcinomas ( hccs )   ( fig . 7 ) . on mri , these lesions usually are t1 hypointense and t2 hyperintense with heterogeneous enhancement ( fig .  8) . hepatobiliary contrast ( gadoxetate disodium , primovist ; bayer healthcare , leverkusen , germany ) could be of help to differentiate hcc from imts of the liver . on the hepatobiliary phase , high signal intensity in the centre of the lesion has been described , suggesting a benign lesion.fig . well - defined , hypointense lesion on t1-weighted images ( a ) which presented weak enhancement in the arterial phase ( b ) and wash - out on portal and equilibrium phases ( c- , d ) located in hepatic left lobe . f the lesion demostrated an expansive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . a abdominal ultrasound where a slightly hypoechoic , solid , heterogeneous mass arising in the left hepatic lobe was observed . axial t1-weighted unenhanced ( b ) and contrast - enhanced mr images ( c , d ) showed an ill - defined with heterogeneous enhancement mass located in lateral hepatic segments . mesenchymal tumour composed of fusiform cells , lymphocytes and lipid - filled macrophages can be observed . normal hepatocytes with large and small fatty droplet change are also present pathology : imt of the liver . well - defined , hypointense lesion on t1-weighted images ( a ) which presented weak enhancement in the arterial phase ( b ) and wash - out on portal and equilibrium phases ( c- , d ) located in hepatic left lobe . e macroscopic view of partial hepatectomy obtained after surgical excision of the lesion . a solid , well - defined and yellowing appearance mass is showed . f the lesion demostrated an expansive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . a abdominal ultrasound where a slightly hypoechoic , solid , heterogeneous mass arising in the left hepatic lobe was observed . axial t1-weighted unenhanced ( b ) and contrast - enhanced mr images ( c , d ) showed an ill - defined with heterogeneous enhancement mass located in lateral hepatic segments . mesenchymal tumour composed of fusiform cells , lymphocytes and lipid - filled macrophages can be observed . normal hepatocytes with large and small fatty droplet change are also present surgery is the most accepted treatment . if there is a biopsy - proven diagnosis of imts that excludes malignancy , medical treatment with no steroidal anti - inflammatory drugs in patients with peripheral hepatic imts could be prescribed . patients with spleen imts frequently associate unspecific symptoms as left upper quadrant or epigastric pain . splenomegaly is common and some patients can present fever , anaemia and signs of hypersplenism . different radiological imaging modalities have been proposed for their evaluation . on all of them , they are depicted as low - density masses in both non - enhanced and enhanced acquisitions ( fig . 9 ) . on mri studies , they present low - intensity mass on both the t1- and t2-weighted images . their typical enhancement pattern after gadolinium injection is as a low - intensity lesion in the early phase , which changes into a high - intensity one in the delayed phase .fig . 9pathology : imt of the spleen . a axial reformation of contrast - enhanced ct on portal phase . prominent cellularity composed of an irregular , weakly basophil set of mioepithelial - fusiform cells . numerous inflammatory cells ( plasmatic , lymphocytes and few neutrophils and eosinophils ) with isolated macrophages were also found . no atypia or mitotic figures were present pathology : imt of the spleen . a axial reformation of contrast - enhanced ct on portal phase . prominent cellularity composed of an irregular , weakly basophil set of mioepithelial - fusiform cells . numerous inflammatory cells ( plasmatic , lymphocytes and few neutrophils and eosinophils ) with isolated macrophages were also found . no atypia or mitotic figures were present the differential diagnosis includes splenic haemangioma and other primary splenic neoplasms such as lymphoma or splenic angiosarcoma . when a suspicious spleen mass is found , the treatment of choice is splenectomy due to the high risk of bleeding associated to splenic biopsy [ 8 , 31 ] . they can arise anywhere , the stomach and small intestine being the most common locations [ 3 , 9 ] . clinical symptoms may vary from none to abdominal pain , intestinal obstruction , dysphagia or anaemia , depending on the location and size of the mass . contrast - enhanced ct is the imaging technique , which give us more information about of imts of the gastrointestinal tract . they are usually found as hypodense , heterogeneous and well - delimited masses ( figs . axial reformation of contrast - enhanced ct on arterial ( a ) , portal ( b ) and 3 min after injection delayed ( c ) acquisitions . a well - defined , heterogeneous nodule with moderate enhancement on portal phase arising from the gastric fundus was found ( yellow arrows ) . d microscopic studies performed after surgical removal of the lesion demonstrated high amount of mesenchymal fusiform cells combined with vascular structures . axial and coronal reformations of contrast - enhanced ct on portal ( a , b ) and 8 min after injection delayed acquisitions ( c , d ) . pararectal solid and well - defined mass with moderated peripheral enhancement adjacent to the rectum and left seminal vesicle was detected . mesenchymal neoplasm composed of polygonal cells with clear cytoplasm and round normochromatic nuclei with abundant vessels and occasional scattered inflammatory cells was observed . mixed within the neoplasm cells , there was a chronic inflammatory infiltrate of lymphoid cells . 12pathology : metastatic imt of the appendix . a 63-year - old man with antecedents of left hemicolectomy due to colon cancer . a axial reformation of contrast - enhanced ct on portal phase acquired seven years after partial colectomy . an appendicular , irregular , solid mass with slight enhancement was identified ( yellow arrow ) . due to its radiological features , b axial reformation of contrast - enhanced ct on portal phase performed 8 months later showed a significant growth of the appendicular mass with extension and infiltration of the adjacent small bowel loops . axial reformation of contrast - enhanced ct on arterial ( a ) , portal ( b ) and 3 min after injection delayed ( c ) acquisitions . a well - defined , heterogeneous nodule with moderate enhancement on portal phase arising from the gastric fundus was found ( yellow arrows ) . d microscopic studies performed after surgical removal of the lesion demonstrated high amount of mesenchymal fusiform cells combined with vascular structures . the lesion showed well - defined contours and an expansive growth pattern pathology : pararectal imt . axial and coronal reformations of contrast - enhanced ct on portal ( a , b ) and 8 min after injection delayed acquisitions ( c , d ) . pararectal solid and well - defined mass with moderated peripheral enhancement adjacent to the rectum and left seminal vesicle was detected . mesenchymal neoplasm composed of polygonal cells with clear cytoplasm and round normochromatic nuclei with abundant vessels and occasional scattered inflammatory cells was observed . mixed within the neoplasm cells , there was a chronic inflammatory infiltrate of lymphoid cells . there were no foci of necrosis or mitotic figures pathology : metastatic imt of the appendix . a 63-year - old man with antecedents of left hemicolectomy due to colon cancer . a axial reformation of contrast - enhanced ct on portal phase acquired seven years after partial colectomy . an appendicular , irregular , solid mass with slight enhancement was identified ( yellow arrow ) . due to its radiological features , b axial reformation of contrast - enhanced ct on portal phase performed 8 months later showed a significant growth of the appendicular mass with extension and infiltration of the adjacent small bowel loops . c distant lymphadenopathy and liver metastases were present the differential diagnosis of these tumours includes gist , inflammatory fibroid polyp , smooth muscle neoplasm , peripheral nerve sheath tumour , solitary fibrous tumour , fibromatosis , the follicular dendritic cell sarcoma , lymphoma and adenocarcinomas . in most of these cases imts of the gastrointestinal tract present a higher recurrence rate than in other locations of the body . other treatments , such as steroids , non - steroidal anti - inflammatory drugs and thalidomide , have been used in these tumours . radiotherapy may have a place as adjunctive therapy in local recurrence and incomplete surgical removal . imts of the appendix are extremely rare , with few cases reported in the literature [ 9 , 33 , 34 ] . chronic infections , antecedents of trauma or surgery have been proposed as possible aetiological factors . extremely rare cases of imts of the appendix showing local aggressiveness and metastases have been reported   ( fig . many different aetiological factors have been proposed for mesenteric imts [ 37 , 38 ] , such as chronic infections , autoimmune diseases and trauma . on contrast - enhanced ct they usually appear as solid masses with heterogeneous enhancement pattern and ill- or well - defined margins . they are often associated with a general inflammatory response manifested with fever , weight loss and other symptoms that are related to the compressive effect of the tumour , such as abdominal pain and vomiting . rapidly growing tumours or symptomatic ones needing treatment may follow from small tumours which are not encroaching any nearby structures . different treatments have been proposed : non - steroidal anti - inflammatories , anti - oestrogens , chemotherapeutic agents and surgery . surgery remains as a useful modality although quite a high local recurrence rate has been described for tumours [ 3 , 37 , 38 ] . the symptoms that most often appear include pain , haematuria , dysuria or urinary tract obstruction . the radiological features do not help to distinguish them from malignant neoplasms , such as rabdomyosarcomas ( fig . , fine - needle biopsy may fail to yield a sufficient volume of tumour tissue to achieve diagnosis.fig . a axial and b coronal reformations of contrast - enhanced ct where an ill - defined and heterogeneous mass encompassing iliopsoas muscle and external iliac vessels , mimicking malignant sarcomatous neoplasm was observed . proliferation of fibroblast with a diffuse infiltration of lymphocytes , eosinophils and macrophages were found . the mass was well - defined and no signs of invasiveness were found pathology : imt of the iliopsoas muscle . a axial and b coronal reformations of contrast - enhanced ct where an ill - defined and heterogeneous mass encompassing iliopsoas muscle and external iliac vessels , mimicking malignant sarcomatous neoplasm was observed . proliferation of fibroblast with a diffuse infiltration of lymphocytes , eosinophils and macrophages were found . no mitotic figures or cellular atypia were present . imts have been reported in various sites in the head and neck such as bucal space , maxillary sinus , nasal cavity , parotid gland , nasopharynx and larynx ( fig . 1pathology : imt in the left supraglottic space ( arrow ) with paraglottic space involvement indicated by replacement of the paraglottic fat with soft tissue . a axial reformation of contrast - enhanced neck ct . a solid , well - defined , normal tissue was present in the peripheral zone ( * ) pathology : imt in the left supraglottic space ( arrow ) with paraglottic space involvement indicated by replacement of the paraglottic fat with soft tissue . a axial reformation of contrast - enhanced neck ct . a solid , well - defined , little - enhancing nodule in the supraglottic larynx was observed ( yellow arrow ) . b microscopic study obtained after surgical removal of the lesion . the sample showed proliferation of fusiform cells mixed with macrophages and giant multinucleated cells . normal tissue was present in the peripheral zone ( * ) however , the orbit is the most common location of imts . they account for approximately 10  % of orbital masses , being the third most common cause of orbital masses . their aetiology is unknown , but they have been associated with inmunological disorders , different infections and history of trauma . recently , they have been strongly associated with the igg4-related sclerosing systemic inflammatory disease   and with chronic infection by epstein - barr virus . the clinical presentation and symptoms may vary with the location , extension and aggressiveness of the tumour . patients with imts of the orbit can present local symptoms as pain , redness , oedema , proptosis , ptosis , oculomotor deficits , diplopia , lid swelling or mass - effect and systemic symptoms due to the general inflammatory disorders they are frequently associated with . mri is superior to ct in the evaluation of inflammation of the nerves and muscles . they usually appear as solid and heterogeneous enhancing masses , which can affect retro bulbar fat , cause bone destruction , and present intracranial extension . when they show low intensity on t2-weighted images prominent , fibrotic composition is present ( fig . a , b axial and coronal mr reformations of the same patient on t2-weighted sequences showed a well - delimited , hyperintense intraorbital mass , in the intraconal compartment , in the medial aspect . c , d t1-weighted images demonstrated a hypointense , homogeneous , well - delimited mass with peripheral enhancement after gadolinium injection . f microscopic sample obtained after surgery demonstrated an epithelial tumour composed of fusiform cells mixed with an extensive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . in the peripheral of the sample a , b axial and coronal mr reformations of the same patient on t2-weighted sequences showed a well - delimited , hyperintense intraorbital mass , in the intraconal compartment , in the medial aspect . c , d t1-weighted images demonstrated a hypointense , homogeneous , well - delimited mass with peripheral enhancement after gadolinium injection . f microscopic sample obtained after surgery demonstrated an epithelial tumour composed of fusiform cells mixed with an extensive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . in the peripheral of the sample striated muscle cells were also observed pathologically , imts of the head and neck consist of many fibroblastic cells , fibroblastic cells and inflammatory cells , which include plasma cells and eosinophils . the differential diagnosis includes granulomatous diseases , primary infection , sarcoid , sjgren disease , primary and secondary tumours of the orbit , lymphoma and connective tissue diseases . the administration of corticosteroids an inmunosupresors usually leads to a decrease of size of the mass but also radiotherapy or surgery may be indicated . . they account for around the 50  % of benign pulmonary masses in children , representing only about 0.7  % of all tumours of the lung in general population . as in other organs , they are also associated with immunological disorders   and chronic infections . sometimes , imts are also related with antecedents of lung surgery and they can arise in surgical lung scars . common clinical characteristics include unspecific respiratory symptoms , such as cough , chest pain , dyspnea , haemoptysis and unspecific inflammatory symptoms as fever , malaise and weight loss . they usually appear as solitary , well - circumscribed peripheral lung masses , with predominance for the lower lobes   ( fig . on ct with intravenous contrast , they present a variable heterogeneous or homogeneous degree of enhancement pattern [ 3 , 21 ] . it has been described an aggressive behaviour with invasion of the adjacent structures . on mri because of their similar radiological appearance to malignant lung masses , biopsy is necessary to obtain the diagnosis.fig . a 55-year - old man with a cough and haemoptysis.a axial reformation of non - contrast ct with mediastinum window . two solid , ill - defined nodules in right lower lobe are observed ( yellow arrows ) . b axial reformations with lung window of the same patient where the lung nodules are shown ( white arrows ) . c partial lobectomy of the right lower lobe specimen . note the presence of the nodules ( * ) . d microscopic study of the resected lung sample where fusiform cells with an associated inflammatory infiltrate of lymphocytes , plasmatic cells and histiocytes was found pathology : imt of the lung . a 55-year - old man with a cough and haemoptysis.a axial reformation of non - contrast ct with mediastinum window . two solid , ill - defined nodules in right lower lobe are observed ( yellow arrows ) . note the air brocogram observed in the biggest mass . b axial reformations with lung window of the same patient where the lung nodules are shown ( white arrows ) . d microscopic study of the resected lung sample where fusiform cells with an associated inflammatory infiltrate of lymphocytes , plasmatic cells and histiocytes was found the treatment of choice of lung imts is surgery to exclude malignancy and to achieve the cure . although spontaneous regression may occur , local expansion may cause significant morbidity and occasional death . the prognosis after complete surgical resection is excellent , with a low rate of recurrence . in these cases , alternative treatments ( radiotherapy , corticoids or chemotherapy ) to surgery could be also used . the most common presentation of epididymal ( fig .  4 ) and paratesticular imts is a lump in the scrotum.fig . 4pathology : imt of the epididymus . a 40-year - old man with a lump in the scrotum . a a hypoechoic a diffuse infiltrate composed of fibroblastic and fusiform cells mixed with inflammatory cells ( mainly lymphocytes and macrophages ) was observed pathology : imt of the epididymus . a 40-year - old man with a lump in the scrotum . a a hypoechoic , well - delimited epididymal lesion in the right scrotum was detected . a diffuse infiltrate composed of fibroblastic and fusiform cells mixed with inflammatory cells ( mainly lymphocytes and macrophages ) was observed in the evaluation of scrotal masses , us is the most accurate imaging technique , helping to distinguish intratesticular from extratesticular lesions and solid from cystic lesions . on ct , they appear as well - defined , hypodense masses with little enhancement after intravenous contrast injection . in some cases , a 34-year - old man with no relevant medical history came to our hospital with a lump in the scrotum . a us showed an isoechoic , solid , paratesticular nodule with fine calcifications ( yellow arrow ) . b axial reformation of contrast - enhanced ct on portal phase demonstrated a well - delimited , heterogeneous , little - enhancing mass in the right scrotum . d microscopic study of the lesion demonstrated a well - delimited lesion constituted of fibroblasts , lymphocytes and plasmatic cells with associated lymphoid follicle . a 34-year - old man with no relevant medical history came to our hospital with a lump in the scrotum . a us showed an isoechoic , solid , paratesticular nodule with fine calcifications ( yellow arrow ) . b axial reformation of contrast - enhanced ct on portal phase demonstrated a well - delimited , heterogeneous , little - enhancing mass in the right scrotum . d microscopic study of the lesion demonstrated a well - delimited lesion constituted of fibroblasts , lymphocytes and plasmatic cells with associated lymphoid follicle . there was no evidence of adjacent testicle invasion surgical resection without orchiectomy is the ideal treatment , but in some cases the testicle must be removed due to the size of the mass or when the mass is attached to the testis . imts of the penis are extremely rare . to our knowledge , no imts at this location have been reported . we have recorded only one case in our institution ( fig .  6 ) . on ct , this tumour appeared as a well - defined , little - enhancing and non - aggressive mass surrounding the penile urethra and the corpora cavernosa with no evidence of invasion of them.fig . a 46-year - old man with a mass in the penis came to our hospital . he related more than 6 years of slow growth of the mass with no suspicious associated symptoms . c , d axial and coronal reformations of enhanced - ct after the injection of intravenous contrast on portal phase . macroscopic view showed an heterogeneous aspect due to the mixture of tissues ( solid tumour , lipoid component and areas of haemorrhage ) . f microscopic study confirmed a mesenchymal tumour composed of fusiform cells , some of them multinucleated , with round or elongate nucleus . a 46-year - old man with a mass in the penis came to our hospital . he related more than 6 years of slow growth of the mass with no suspicious associated symptoms . c , d axial and coronal reformations of enhanced - ct after the injection of intravenous contrast on portal phase . macroscopic view showed an heterogeneous aspect due to the mixture of tissues ( solid tumour , lipoid component and areas of haemorrhage ) . f microscopic study confirmed a mesenchymal tumour composed of fusiform cells , some of them multinucleated , with round or elongate nucleus . no mitotic figures were observed surgical treatment was performed due to the size and non - conclusive radiological features of the tumour . hepatic imts constitute an extremely rare group of hepatic tumours , accounting only for the 0.7  % of all the hepatic lesions . they have been associated with autoimmune diseases , immunological disorders and viral infections , such as igg4 disease , sclerosing cholangitis , crohns disease , hepatic viral infections   and epstein - barr virus . on contrast - enhanced ct , they usually show heterogeneous or peripheral enhancement during the arterial phase . despite this , some of them present homogeneous enhancement during the arterial phase and washout during the delayed phase , which can lead to misdiagnosing them as hepatocarcinomas ( hccs )   ( fig .  7 ) . on mri , these lesions usually are t1 hypointense and t2 hyperintense with heterogeneous enhancement ( fig .  8) . hepatobiliary contrast ( gadoxetate disodium , primovist ; bayer healthcare , leverkusen , germany ) could be of help to differentiate hcc from imts of the liver . on the hepatobiliary phase , high signal intensity in the centre of the lesion has been described , suggesting a benign lesion.fig . well - defined , hypointense lesion on t1-weighted images ( a ) which presented weak enhancement in the arterial phase ( b ) and wash - out on portal and equilibrium phases ( c- , d ) located in hepatic left lobe . f the lesion demostrated an expansive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . a abdominal ultrasound where a slightly hypoechoic , solid , heterogeneous mass arising in the left hepatic lobe was observed . axial t1-weighted unenhanced ( b ) and contrast - enhanced mr images ( c , d ) showed an ill - defined with heterogeneous enhancement mass located in lateral hepatic segments . mesenchymal tumour composed of fusiform cells , lymphocytes and lipid - filled macrophages can be observed . normal hepatocytes with large and small fatty droplet change are also present pathology : imt of the liver . well - defined , hypointense lesion on t1-weighted images ( a ) which presented weak enhancement in the arterial phase ( b ) and wash - out on portal and equilibrium phases ( c- , d ) located in hepatic left lobe . e macroscopic view of partial hepatectomy obtained after surgical excision of the lesion . a solid , well - defined and yellowing appearance mass is showed . f the lesion demostrated an expansive chronic inflammatory infiltrate of plasmatic cells , lymphocytes and macrophages . a abdominal ultrasound where a slightly hypoechoic , solid , heterogeneous mass arising in the left hepatic lobe was observed . axial t1-weighted unenhanced ( b ) and contrast - enhanced mr images ( c , d ) showed an ill - defined with heterogeneous enhancement mass located in lateral hepatic segments . mesenchymal tumour composed of fusiform cells , lymphocytes and lipid - filled macrophages can be observed . normal hepatocytes with large and small fatty droplet change are also present surgery is the most accepted treatment . if there is a biopsy - proven diagnosis of imts that excludes malignancy , medical treatment with no steroidal anti - inflammatory drugs in patients with peripheral hepatic imts could be prescribed . patients with spleen imts frequently associate unspecific symptoms as left upper quadrant or epigastric pain . splenomegaly is common and some patients can present fever , anaemia and signs of hypersplenism . different radiological imaging modalities have been proposed for their evaluation . on all of them , they are depicted as low - density masses in both non - enhanced and enhanced acquisitions ( fig . their typical enhancement pattern after gadolinium injection is as a low - intensity lesion in the early phase , which changes into a high - intensity one in the delayed phase .fig . 9pathology : imt of the spleen . a axial reformation of contrast - enhanced ct on portal phase . prominent cellularity composed of an irregular , weakly basophil set of mioepithelial - fusiform cells . numerous inflammatory cells ( plasmatic , lymphocytes and few neutrophils and eosinophils ) with isolated macrophages were also found . no atypia or mitotic figures were present pathology : imt of the spleen . a axial reformation of contrast - enhanced ct on portal phase . prominent cellularity composed of an irregular , weakly basophil set of mioepithelial - fusiform cells . numerous inflammatory cells ( plasmatic , lymphocytes and few neutrophils and eosinophils ) with isolated macrophages were also found . no atypia or mitotic figures were present the differential diagnosis includes splenic haemangioma and other primary splenic neoplasms such as lymphoma or splenic angiosarcoma . when a suspicious spleen mass is found , the treatment of choice is splenectomy due to the high risk of bleeding associated to splenic biopsy [ 8 , 31 ] . they can arise anywhere , the stomach and small intestine being the most common locations [ 3 , 9 ] . clinical symptoms may vary from none to abdominal pain , intestinal obstruction , dysphagia or anaemia , depending on the location and size of the mass . contrast - enhanced ct is the imaging technique , which give us more information about of imts of the gastrointestinal tract . they are usually found as hypodense , heterogeneous and well - delimited masses ( figs . axial reformation of contrast - enhanced ct on arterial ( a ) , portal ( b ) and 3 min after injection delayed ( c ) acquisitions . a well - defined , heterogeneous nodule with moderate enhancement on portal phase arising from the gastric fundus was found ( yellow arrows ) . d microscopic studies performed after surgical removal of the lesion demonstrated high amount of mesenchymal fusiform cells combined with vascular structures . axial and coronal reformations of contrast - enhanced ct on portal ( a , b ) and 8 min after injection delayed acquisitions ( c , d ) . pararectal solid and well - defined mass with moderated peripheral enhancement adjacent to the rectum and left seminal vesicle was detected . e macroscopic view of the tumour after surgical resection . f histological sample obtained after biopsy . mesenchymal neoplasm composed of polygonal cells with clear cytoplasm and round normochromatic nuclei with abundant vessels and occasional scattered inflammatory cells was observed . mixed within the neoplasm cells , there was a chronic inflammatory infiltrate of lymphoid cells . 12pathology : metastatic imt of the appendix . a 63-year - old man with antecedents of left hemicolectomy due to colon cancer . a axial reformation of contrast - enhanced ct on portal phase acquired seven years after partial colectomy . an appendicular , irregular , solid mass with slight enhancement was identified ( yellow arrow ) . due to its radiological features , b axial reformation of contrast - enhanced ct on portal phase performed 8 months later showed a significant growth of the appendicular mass with extension and infiltration of the adjacent small bowel loops . axial reformation of contrast - enhanced ct on arterial ( a ) , portal ( b ) and 3 min after injection delayed ( c ) acquisitions . a well - defined , heterogeneous nodule with moderate enhancement on portal phase arising from the gastric fundus was found ( yellow arrows ) . d microscopic studies performed after surgical removal of the lesion demonstrated high amount of mesenchymal fusiform cells combined with vascular structures . the lesion showed well - defined contours and an expansive growth pattern pathology : pararectal imt . axial and coronal reformations of contrast - enhanced ct on portal ( a , b ) and 8 min after injection delayed acquisitions ( c , d ) . pararectal solid and well - defined mass with moderated peripheral enhancement adjacent to the rectum and left seminal vesicle was detected . mesenchymal neoplasm composed of polygonal cells with clear cytoplasm and round normochromatic nuclei with abundant vessels and occasional scattered inflammatory cells was observed . mixed within the neoplasm cells , there was a chronic inflammatory infiltrate of lymphoid cells . there were no foci of necrosis or mitotic figures pathology : metastatic imt of the appendix . a 63-year - old man with antecedents of left hemicolectomy due to colon cancer . a axial reformation of contrast - enhanced ct on portal phase acquired seven years after partial colectomy . an appendicular , irregular , solid mass with slight enhancement was identified ( yellow arrow ) . due to its radiological features , b axial reformation of contrast - enhanced ct on portal phase performed 8 months later showed a significant growth of the appendicular mass with extension and infiltration of the adjacent small bowel loops . c distant lymphadenopathy and liver metastases were present the differential diagnosis of these tumours includes gist , inflammatory fibroid polyp , smooth muscle neoplasm , peripheral nerve sheath tumour , solitary fibrous tumour , fibromatosis , the follicular dendritic cell sarcoma , lymphoma and adenocarcinomas . in most of these cases imaging features are not enough to diagnose imts and biopsy or surgery are needed . imts of the gastrointestinal tract present a higher recurrence rate than in other locations of the body . other treatments , such as steroids , non - steroidal anti - inflammatory drugs and thalidomide , have been used in these tumours . radiotherapy may have a place as adjunctive therapy in local recurrence and incomplete surgical removal . imts of the appendix are extremely rare , with few cases reported in the literature [ 9 , 33 , 34 ] . chronic infections , antecedents of trauma or surgery have been proposed as possible aetiological factors . extremely rare cases of imts of the appendix showing local aggressiveness and metastases have been reported   ( fig . many different aetiological factors have been proposed for mesenteric imts [ 37 , 38 ] , such as chronic infections , autoimmune diseases and trauma . on contrast - enhanced ct they usually appear as solid masses with heterogeneous enhancement pattern and ill- or well - defined margins . they are often associated with a general inflammatory response manifested with fever , weight loss and other symptoms that are related to the compressive effect of the tumour , such as abdominal pain and vomiting . rapidly growing tumours or symptomatic ones needing treatment may follow from small tumours which are not encroaching any nearby structures . different treatments have been proposed : non - steroidal anti - inflammatories , anti - oestrogens , chemotherapeutic agents and surgery . surgery remains as a useful modality although quite a high local recurrence rate has been described for tumours [ 3 , 37 , 38 ] . the symptoms that most often appear include pain , haematuria , dysuria or urinary tract obstruction . the radiological features do not help to distinguish them from malignant neoplasms , such as rabdomyosarcomas ( fig . , fine - needle biopsy may fail to yield a sufficient volume of tumour tissue to achieve diagnosis.fig . a axial and b coronal reformations of contrast - enhanced ct where an ill - defined and heterogeneous mass encompassing iliopsoas muscle and external iliac vessels , mimicking malignant sarcomatous neoplasm was observed . proliferation of fibroblast with a diffuse infiltration of lymphocytes , eosinophils and macrophages were found . no mitotic figures or cellular the mass was well - defined and no signs of invasiveness were found pathology : imt of the iliopsoas muscle . a axial and b coronal reformations of contrast - enhanced ct where an ill - defined and heterogeneous mass encompassing iliopsoas muscle and external iliac vessels , mimicking malignant sarcomatous neoplasm was observed . proliferation of fibroblast with a diffuse infiltration of lymphocytes , eosinophils and macrophages were found . no mitotic figures or cellular although imts in some organs are not uncommon , they are not usually included in the differential diagnosis of nodules and masses . consequently , this is an underdiagnosed entity and only after an histological exam could definitive diagnosis be achieved . it is fundamental for radiologists to know about the existence of imts , as they frequently have better treatment options and prognosis than the malignant neoplasms they are confused with .