Uncommon Diagnostic Pitfalls of Mucoepidermoid Carcinoma on Cytology: A Tertiary Care Center, Retrospective Descriptive Study

Introduction: Diagnosis of mucoepidermoid carcinoma (MEC) on fine-needle aspiration cytology (FNAC) is grim with important diagnostic pitfalls, leading to wrong treatment decisions. This study highlights uncommon mimics of MEC on FNAC smears of major salivary glands and compares the cytologic findings with definitive histopathology diagnosis for identification of potential diagnostic pitfalls. Methods: This is a retrospective descriptive study of MEC cases diagnosed over a duration of 5 years (April 2015-April 2020) at a tertiary care center with available preoperative FNAC and postoperative histopathology resection specimens. Results: Out of a total of 18 MEC cases diagnosed by histopathologic examination, 8 (44%) were wrongly diagnosed on preoperative FNAC as a different benign or malignant entity. Further details of these cases are shared in the text. Discussion: Although FNAC remains an important preoperative diagnostic tool in salivary gland lesions, utmost care is required in the cases of MEC which are notorious for misinterpretation on cytology. A number of uncommon mimics, both benign and malignant, need to be considered and carefully excluded to spare the patient of avoidable miseries of misdiagnosis. Conclusion: MECs of salivary glands can mimic the morphology of a variety of benign as well as malignant lesions on cytology with low cyto-histologic concordance especially in cystic lesions.