Clinicopathologic Features of Epithelial Myoepithelial Carcinoma of the Head and Neck: Analysis of Demographics, Clinical Characteristics, and Treatment Modality

Purpose: Epithelial myoepithelial carcinoma (EMC) is a rare salivary gland malignancy that accounts for less than 1% of salivary gland tumors. Our study evaluates clinicopathologic features of the largest known cohort reported in current literature. Methods: We queried the Surveillance, Epidemiology, and End Results (SEER) database for cases reported between 2000-2018. Demographic and clinicopathologic data were collected, and Cox proportional hazards survival analysis was performed to evaluate for factors impacting overall survival (OS) and cause-specific survival (CSS). Results: Three-hundred eighty-six cases with a median age of 66 were included. EMC was found to occur predominantly in females (56.5%) and in Caucasians (77.6%). Two-hundred forty-seven (71.4%) of cases were localized to the primary site, while 76 (22.0%) had regional disease, and 23 (6.6%) had distant metastases. The majority of patients received surgery monotherapy (51.6%) or surgery with radiation (41.7%). The treatment modality with the highest 5-year CSS was surgery monotherapy (90.9%, 95% Confidence Interval (CI) = 88.1-93.7, p = 0.780). Univariate analysis revealed that increased age, high grade, tumor size of >4.1cm, regional, and distant stage were independent factors that led to poorer prognosis in CSS. Multivariate analysis revealed that increasing age (HR=1.08, 95% CI=1.06-1.11, p <0.001), high grade (HR=11.35, 95% CI=3.35-38.45, p<0.001), and distant stage (HR=7.63, 95% CI=2.00-29.10, p = 0.003) negatively impacted survival is CSS. Conclusion: EMC mainly affects older Caucasian females. Independent variables that led to worse CSS were advanced age, high tumor grade, larger tumor size, and regional and distant stage. Five-year OS and CSS were generally favorable with surgical therapy.