Pathologic Grading of Mucoepidermoid Carcinomas of the Salivary Gland and its Effect on Clinicopathologic Follow-up: An Institutional Experience

Abstract Background Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor. Differences in prognosis can be noted due to tumor grade using multiple grading schemes (2 tier: low and high grade vs. 3 tier: low, intermediate and high grade). We studied clinicopathologic features of MEC using a 3-tier grading system and retrospectively categorized cytologic diagnoses according to the Milan System for Reporting Salivary Gland Cytology (MSRSGC). Methods 69 cases of MEC were identified, most were seen in the parotid gland. Results Aggressive clinical behavior was seen in the high grade MEC compared to the intermediate and low grade MEC. By FISH analysis MAML2 rearrangements were seen in 78% of cases. Conclusions The MSRSGC subcategorized the majority (63.8%)of MEC as SUMP, suspicious for malignancy or malignant. Clustering intermediate with low grade cases did not significantly impact the clinical behavior. Both high grade and oncocytic MEC can be MAML2 FISH negative.