The cytologic diagnosis of Mucoepidermoid carcinoma ( esp the low grade) is challenging, due to overlapping cytomorphology with benign lesions . High grade neoplasm on the other hand can be easily recognized as malignant based on tumour necrosis, nuclear pleomorphism and high mitotic activity. Oncocytic variant of mucoepidermoid carcinoma (OMEC) is rare. To label it as OMEC, tumour must be composed of 50 percent or more of oncocytic cells1. A diffuse nuclear staining from p63 immunostaining is done for diagnosis of OMEC. FISH detection of MAMC2 gene translocation detection is of great value in its diagnosis2.

A 28 year old male presented with swelling in right parotid for last 2 years. The swelling was painless and of the size of a pea and gradually increased to the size of an orange .There is no past history of DM, HTN, and any other co morbidities. On examination 2*2 cm oral subcutaneous swelling in right parotid region is present, firm in consistency and mobile (IMAGE 1). There is no local rise of temperature and no tenderness. No scar mark is present. No cervical lymphadenopathy is present. Skin above the swelling is smooth.

The specimen was sent for histopathological examination which established the diagnosis (IMAGE 4). Polygonal oncocytes seen in a densely fibrous stroma. Intermediate cells with interspersed mucocytes seen along with granular cytoplasm and distinct cell membrane borders. The patient was in regular follow up for 6 months with proper healing and no sign of recurrence.

Mucoepidermoid carcinoma is the most common type of salivary gland cancers. It accounts for 5 to 10 percent of all salivary gland neoplasms3 .It is mostly seen in parotid. FNAC accessibility is feasible for this reason. MEC is formed by 3 principal cell types - squamous, mucinous, and intermediate. MEC has other morphological variants OMEC, Sebaceous cells, Spindle cells, Goblet cells and Clear cells. Oncocytic variant is very rare. To label it as oncocytic, tumour should consist of > 50 percent oncocytic cells. MEC classified into low grade and high grade4. High grade can still be differentiated based on clinical features like facial nerve palsy, deep fixation, lymphadenopathy and cytological findings like tumour necrosis and nuclear pleomorphism5. On the contrary low grade MEC is difficult to diagnose because of overlapping features and clinical similarities with other parotid neoplasm6. Differential diagnosis of OMEC are oncocytoma and oncocytic carcinoma. Oncocytomas are usually seen in elderly. Mostly in females in 6th and 7th decade7. It affects parotid gland in 80 percent cases8. They are benign neoplasm with well circumscribed mass, composed of layers of oncocytes with no mitotic figures9. They are described as large round cells with abundant granular cytoplasm10. They are slow glowing tumours. Oncocytic carcinoma are very rare, mostly seen in males and affects parotid and submandibular gland. They are high grade tumours seen after radiotherapy. On Histopathology they show adenocarcinoma type features, infiltrative growth, mucus production, perineural invasion, atypia and mitotic figures11. OMEC on other hand is low to intermediate grade malignancy . They consist of predominantly oncocytes with small number of mucocytes. Diagnosis of OMEC is very challenging. p63 immunostaining and MAML2 gene translocation useful tool for its diagnosis12.

OMEC is a rare tumour and they are mostly seen in parotids with female’s preponderance. High degree of suspicion is required for its diagnosis with stress on histopathological findings and immunostaining. Treatment is surgical excision with follow up for recurrence and radiotherapy in case of perineural invasion.

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