Intraoral Oncocytic Mucoepidermoid Carcinoma - A Rare Case Report and Review of the Literature

RATIONALE: Oncocytic mucoepidermoid carcinoma (OMEC) is a rare variant of mucoepidermoid carcinoma (MEC). The parotid gland is the most common site of OMEC, whereas intraoral OMEC is infrequent. PATIENT CONCERNS: A 55-year-old male presented with an asymptomatic mass at the palate for 20 years. DIAGNOSIS: Incisional biopsy showed classic MEC. TREATMENT: The patient underwent partial maxillectomy under general anaesthesia. The excised specimen revealed sheets of oncocytes additional to the tumour cells found in the incisional biopsy. Additional special stain and immunohistochemical stain confirmed the diagnosis of OMEC. OUTCOMES: The patient was followed up for 3 years with no recurrence. TAKE-AWAY LESSONS: The diagnosis of OMEC needs to be differentiated from other salivary gland tumours containing oncocytes. Moreover, the conventional grading system applied to OMEC may not correlate with their behavior and may need further review.