Rapid On-site Evaluation (ROSE) Cytology of Mucoepidermoid Carcinoma and its Diagnostic Pitfalls: a Case Report

Fine needle aspiration cytology (FNAC) is a basic tool used for the preoperative diagnosis of superficial parotid swellings. Mucoepidermoid carcinoma accounts for approx. 5-10% of all salivary gland tumors. However, due to its morphologic heterogenicity, this tumor poses diagnostic difficulties in its interpretation. This is a case of a 45-year-old male with a history of recurrent swelling in the left infra-auricular region. Cytology with rapid on-site evaluation revealed a triphasic population of basaloid cells, squamoid cells, and intermediate cells on a mucoid background and reported as low-grade mucoepidermoid carcinoma in recurrence. The presence of a triphasic cellular component (mucous, intermediate, and squamoid cells) may not be seen in all cases of mucoepidermoid carcinoma (MEC) for definitive diagnosis. Clinico-radiological correlation, rapid on-site evaluation (ROSE), and high index of suspicion related to cystic lesions are important for early diagnosis and prompt treatment.