a 65-year - old male patient visited the department of oral medicine of the institute for getting his missing teeth replaced . on intraoral clinical examination of the patient , a deep red - colored multinodular but small swelling ( measuring 1.5 cm  2 cm  2 cm ) was observed in the left posterior palatal region ( missing 26 , 27 , 28 ) extending toward the midline [ figure 1 ] .
as per the patient 's information , the swelling was observed nearly 6 months back and was found to be gradually increasing .
on palpation , the mass was firm and fixed to the underlying tissues . neither loosening of teeth nor tenderness on percussion was noted .
orthopantomograph and occlusal radiograph did not reveal any significant bone changes , suggesting that the lesion was still superficial [ figure 2 ] .
the patient was diabetic for the last 22 years and was on medication for the same .
the solitary , firm , asymptomatic , and nonulcerated mass seen on the palate instantly suggested a benign salivary gland tumor . clinical differential diagnoses included benign lymphoepithelial lesion or mucus extravasation phenomena .
however , we also considered malignancies such as malignant salivary gland tumor , lymphoma , and neoplasm of the maxillary sinus as the possible diagnoses . incidentally
, our patient did not complain of swelling or discomfort ; in fact , the patient 's visit to the hospital was aimed at getting his missing teeth replaced .
the most commonly observed benign salivary gland tumors on the palate include pleomorphic adenoma ( pa ) and basal cell adenoma .
pa , also known as mixed tumor , is the most common tumor of the major and minor salivary glands , more prevalent in elderly males .
intraorally , palate is the most common site where they appear as firm , painless swellings , and in the vast majority of cases , they do not cause ulceration of the overlying epithelium .
pa is typically lobulated and enclosed within a connective tissue pseudocapsule that varies in thickness within the major salivary glands , whereas in minor salivary glands , the capsule is poorly defined to absent in areas .
. they account for approximately 34% of parotid malignancies , 20% of submandibular gland malignancies , and 30% of minor salivary gland malignancies , with palate as the most common intraoral site .
since there was no pain , paresthesia , or ulceration , the possibility of mucoepidermoid carcinoma was ruled out .
lymphoma was considered plausible as the swelling was asymptomatic , showing spongy to firm tumescence ; these features simulated our case .
the clinical presentation of lymphomas of the oral region varies with their site of origin and tumor type , but most present as a mass or an ulcerated mass and resemble squamous cell carcinoma or salivary neoplasm . within the oral cavity
, lymphoid tissue is chiefly represented in waldeyer 's ring ; elsewhere within the oral cavity , it appears as unencapsulated lymphoid tissue within the base of the tongue and soft palate , as well as within the major and minor salivary glands .
non - hodgkin 's lymphoma ( nhl ) is very often seen on the hard palate , primarily in elderly men and women with an average age of 70 years .
oral lymphomas are relatively rare and often difficult to diagnose in a clinical setting , and most often mimic other pathological entities , such as dentoalveolar abscess , periodontal abscess , infected dental cyst , or benign jaw tumors .
it typically is characterized by swollen and nonpainful enlargement of the lymph nodes , especially at the junction of hard and soft palates .
although lymphoid lesions in the hard palate are very likely to be lymphomas , follicular lymphoid hyperplasia can present in this anatomic location ; hence , a thorough histologic examination is of utmost significance .
histologic differentiation must be made among lymphoid hyperplasia , nhl , and benign lymphoepithelial lesion , when present in the hard palate .
since it was a nodular and nonulcerated swelling , trauma could have also caused the nodule formation because of mucus extravasation caused by the severance of salivary gland excretory duct .
although palate is not the common site of mucus extravasation phenomenon , it usually presents as a relatively painless smooth - surfaced mass ranging in size from a few millimeters to 2 cm in size , consistent with our case . however , our patient reported that the mass was persistent for the last few months , which negated the possibility of a mucocele .
last but not least , even neoplasm of maxillary sinus could be a reason for the palatal swelling .
occasional maxillary sinus cancers may present as a palatal ulcer and mass representing extension through the bone and soft tissue of the palate .
fine needle aspiration cytology of the lesion was done and the smear stained with papanicolaou stain revealed mucin and keratin , which was nonspecific .
histopathology of the specimen revealed parakeratinized stratified squamous epithelium which was hyperplastic at areas with an underlying fibrocellular connective tissue stroma .
the stroma showed unencapsulated , circumscribed tumor mass composed of homogeneous population of cuboidal to columnar isomorphic cells with prominent , bland , often vesicular ovoid to spindle - shaped nuclei and minimal eosinophilic cytoplasm .
the tumor cells were arranged as solid nests , lobules , and glandular patterns extending till the entire depth of the received specimen [ figure 3a and b ] .
few areas of intraluminal mucin and hyalinization of stroma surrounding the tumor cells were evident .
( a ) low power magnification demonstrates parakeratinized stratified squamous epithelium and multiple lobules showing glandular and ductular patterns of tumor cells ( h and e , 40 ) .
( b ) tumor cells display prominent vesiculated appearance of the ovoid nuclei arranged in glandular patterns .
cellular atypia and multiple mitotic figures are also observed ( h and e , 400 ) .
( c ) perineural invasion by tumor cells is evident in focal areas ( 400 )
patient is on a regular follow - up and there is no recurrence reported even after 1 year of follow - up .
histopathologically , the most difficult neoplasms to differentiate from plga are benign mixed tumor and adenoid cystic carcinoma ( acc ) . however ,
furthermore , neither benign mixed tumors do show neurotropism , nor they do demonstrate perivascular , osseous , or cartilaginous infiltration . possibly , acc is the most difficult tumor to differentiate histopathologically from plga .
they are also unencapsulated , infiltrating tumors that have a strong tendency for neural invasion . some other features accs have in common with plgas include the histologic patterns such as cribriform , solid , and tubular .
nevertheless , the distinction between acc and plga can be done based on histologic examination .
for example , the nuclei of acc are more hyperchromatic and more angular than those of plga .
cribriform areas with accumulation of basophilic glycosaminoglycans are observed frequently in acc , not in plga .
moreover , the cytoplasmic staining of plga is eosinophilic to amphophilic , whereas that of acc is very pale to clear staining .
the distinction between acc and plga is important because acc is more aggressive and relentless clinically with multiple recurrences . on the other hand
, plga is an indolent neoplasm where patients are free of the tumor after conservative wide surgical excision , with least requirement of postoperative radiotherapy and chemotherapy .
although considered to be a low - grade malignancy , a case of de novo plga was described which was observed in a minor salivary gland with a large radiographic extent .
plga was earlier referred to as terminal duct carcinoma owing to its probable origin in the ductal system of the salivary glands .
plga is formed by luminal epithelial , myoepithelial , and basal epithelial cells simulating terminal duct carcinoma .
plga is a low - grade malignant neoplasm because of rare occurrence of regional lymph node metastasis , with even extremely rare manifestation of distant metastasis . microscopic or histopathologic observation of perineural invasion does not appear to affect the prognosis .
this neoplasm manifests almost exclusively in minor salivary glands , with a high predilection for the palate .
however , some cases have been reported in major salivary glands , for example , in the parotid gland , where most cases have been diagnosed as part of a carcinoma ex pa , such as those in the case series reported by kemp et al . , who found that only two out of twenty cases arose de novo , and the rest showed remnants of pa .
plgas arising in major salivary glands have clinicopathological and immunohistochemical features similar to those of plgas originating in minor salivary glands .
the tumor , histopathologically , shows a uniform and bland cytological picture , a diverse yet characteristic growth pattern and a prominent neurotropism .
this clinicopathologic entity is , sometimes , a diagnostic dilemma due to its multiple histomorphologic patterns and its cytologic uniformity .
immunohistochemical studies comparing pa and plga have shown that glial fibrillary acidic protein is negative in plga and positive in pa .
however , plga differs from pa because it is characterized by infiltrative margins and an absence of chondromyxoid stroma .
plga presenting as palatal lesion is not so rare and should be included in the differential diagnosis of palatal lesions , presenting as nonulcerated nodular swellings .
other salivary gland malignancies commonly seen on the palate , including mucoepidermoid carcinoma and acc , should also be considered in the differential diagnosis .
it is of prime importance to differentiate among these malignant lesions and reach a conclusive diagnosis as the management and prognosis varies for each of them . while acc is associated with low long - term survival rates , plga is a low - grade malignancy , and its biologic behavior is apparently not influenced by the different morphologic and cell differentiation patterns that it may reveal .
it is of prime importance for a pathologist to inform the predominant histologic pattern in plga , the presence of perineural invasion and vascular permeation , so as to affirm if these criteria are helpful to identify its biologic behavior .
 we present an interesting but intriguing case of an indolent palatal swelling . the lesion was asymptomatic causing little discomfort to the patient and thus was an incidental clinical finding . 
 provisional diagnosis was a benign , minor salivary gland tumor . 
 clinical differential diagnoses included benign lymphoepithelial lesion or mucus extravasation phenomenon . nevertheless , we also considered malignancies such as mucoepidermoid carcinoma , lymphoma , and neoplasm of the maxillary sinus . 
 however , the histopathology revealed a rare clinicopathologic entity prompting immediate treatment of the lesion . 