an inflammatory myofibroblastic tumor ( imt ) is a distinctive neoplasm composed of myofibroblastic and fibroblastic spindle cells accompanied by inflammatory infiltration of plasma cells , lymphocytes , and eosinophils .
it is important to distinguish this tumor from other malignant spindle cell tumors , such as the sarcomatoid variant of urothelial carcinoma and leiomyosarcoma .
we report a case of imt of the urinary bladder in a 52-year - old male diagnosed by transurethral resection of the bladder tumor ( turbt ) treated by partial cystectomy .
his medical history revealed a diagnosis of rheumatoid arthritis 3 years ago , and prednisolone 10 mg / day was subsequently prescribed .
cystoscopy revealed a solitary nonpapillary tumor with surrounding edema at the dome of the bladder ( fig .
1a ) . enhanced computed tomography ( ct ) and magnetic resonance imaging ( mri ) revealed an early enhancing bladder tumor infiltrating the outside of the bladder muscle layer ( fig .
intraoperative findings showed a large solid bladder mass , measuring approximately 3 cm from the dome to the anterior wall of the bladder .
we resected the tumor to the depth of the muscle layer , but normal muscle tissue was not seen .
histopathology results were consistent with an imt . the bladder tissue , including muscle , was widely infiltrated by spindle cells in a myxoid stroma accompanied by infiltration of inflammatory cells ( fig .
immunohistochemical staining was positive for vimentin and smooth muscle actin ( fig . 2c ) and negative for ae1/ae3 , desmin , myogenin , s-100 , cd34 , c - kit , cd68 , and bcl-2 .
the excised specimen is shown in figure 2d . a pathological examination of the excised specimen revealed the proliferation of spindle cells expanding into the bladder musculature , accompanied by inflammatory cell infiltration .
for the assessment of therapeutic options , we measured the expressions of anaplastic lymphoma kinase ( alk ) , vascular endothelial growth factor ( vegf ) , and cyclooxygenase 2 ( cox2 ) , known as growth factors involved in tumor proliferation .
it is characterized by atypical spindle cell proliferation and inflammatory cell infiltrates primarily involving lymphocytes and plasma cells .
although it has been associated with trauma , surgery , and infection , the majority of imt cases occur spontaneously .
imt tumors are classified as intermediate ( rarely metastasizing ) tumors according to the who classification of soft tissue tumors .
imts occur in the mesentery , omentum , retroperitoneum , pelvis , and abdominal soft tissues in 73% of cases .
however , the occurrence of an imt in the urinary bladder is unusual . a systematic review by teoh et al
.   evaluated 182 imt cases and found a mean age of patients of 38.9 years , with a predilection for females .
imts resemble malignant spindle cell tumors , such as sarcomatoid carcinoma , leiomyosarcoma , or rhabdomyosarcoma , making diagnosis difficult .
recent reports have indicated that alk , which was originally identified as a protein overexpressed in anaplastic large - cell lymphomas , was also overexpressed in a substantial proportion of imts [ 5 , 6 ] .
a positive finding of alk by immunohistochemistry in up to 87.5% of imts can be useful for the differentiation of imts from other spindle cell tumors . in this case ,
alk gene translocation in imts has also been reported , for which detection by fluorescence in situ hybridization ( fish ) is useful .
however , performing fish in paraffin - embedded specimens is questionable for obtaining a precise diagnosis .
alk protein expression , as determined by immunohistochemistry , correlates well with the presence of a rearrangement in the alk gene [ 7 , 8 ] .
therefore , we did not undertaken fish analysis in this case because of the strong immunohistochemical positivity of alk . in the consideration of a therapy for imt , surgical resection
, most patients underwent turbt ( 60.8% ) ; others had partial ( 29.2% ) and radical cystectomy ( 9.2% ) , and 5 patients experienced local recurrence .
while partial or radical cystectomy ensures complete resection of imt , turbt is also a considerable choice , given the benign course of an imt . in the present case , ct ,
mri , and the examination of a turbt indicated a muscle layer - infiltrating lesion , so we performed a partial cystectomy .
there were no reports as to the safety margin of imt in the bladder at partial cystectomy .
we performed the operation by setting a margin of about 1 cm , and there was no sign of local recurrence in the bladder wall . for performing the operation while keeping the bladder capacity , further investigation as to the surgical margin
cox2 and vegf expression have been detected in imts and are thought to be therapeutic targets .
additionally , as an anti - inflammatory drug , cox2 inhibitors used for nonresectable imts have often been reported .
an alk inhibitor , crizotinib , has also been used in the treatment of imts . in the present case
, we examined cox2 , vegf , and alk protein expression with immunohistochemistry and found imt tissues to be vegf and alk positive . prednisolone has previously been prescribed in this case .
we also thought that the tumor was resectable by partial cystectomy and therefore decided against a course of pharmacotherapy .
however , in the case of recurrence when the tumor is not resectable , pharmacotherapy may become a viable therapeutic option . in conclusion ,
a typical imt can be locally aggressive and may require radical surgical resection ; close follow - up is therefore warranted .
written informed consent was obtained from the patient for publication of this case report and accompanying images .
a copy of the written informed consent is available for review from the editor - in - chief of this journal .
 an inflammatory myofibroblastic tumor ( imt ) is a distinctive neoplasm composed of myofibroblastic and fibroblastic spindle cells , accompanied by inflammatory infiltration of plasma cells , lymphocytes , and eosinophils . 
 imts rarely occur in the urinary bladder . 
 it is important to distinguish this tumor from other malignant spindle cell tumors . 
 herein , we report a patient with an imt showing muscle invasion , who underwent a transurethral resection of the bladder tumor and , at a later date , partial cystectomy . the resected tumor specimen revealed a proliferation of spindle - shaped cells on a background of plasma cells and lymphocytes . 
 immunohistochemical staining showed the tumor to be positive for anaplastic lymphoma kinase ( alk ) , smooth muscle actin , and vascular endothelial growth factor ( vegf ) . 
 such histopathological findings were indicative of an imt , suggesting the use of inhibitors of alk and vegf as pharmacotherapy . 