Histologic grade as prognostic indicator for mucoepidermoid carcinoma: a population-level analysis of 2400 patients.

BACKGROUND Mucoepidermoid carcinoma (MEC) is an uncommon malignancy. To the best of our knowledge, this is the largest study investigating disease-specific survival (DSS) of parotid MEC and the first population-level study of the distribution of nodal metastases. METHODS Patients with MEC of the parotid gland were identified in the Surveillance, Epidemiology, and End Results (SEER) database (1988-2009). RESULTS We identified 2400 patients with MEC: 522 low grade, 1137 intermediate grade, and 741 high grade. Five-year DSS rates for low-grade, intermediate-grade, and high-grade MEC were 98.8%, 97.4%, and 67.0%, respectively (p < .001). Negative prognostic factors included high grade, increasing patient age, and tumor size, extraparenchymal extension, nodal metastases, and distant metastases. High-grade MEC was more likely to have lymph node metastases in levels I to III (34.0%) than low-grade (3.3%) and intermediate-grade MEC (8.1%; p < .001). CONCLUSION Grade influences the prognosis and distribution of nodal metastases. Results indicate that management guidelines should vary based on grade.