Epithelial-myoepithelial carcinoma: a population-based survival analysis.

Background: Epithelial-myoepithelial carcinoma is an uncommon malignant neoplasm seen most frequently in the salivary glands, representing approximately 1 to 2% of salivary gland tumors. Less than 600 cases have been reported in the literature since its initial description in 1972. The aim of this study was to examine demographic, site, stage, and survival factors in patients with epithelial-myoepithelial carcinoma.

Methods: The 1973-2014 SEER (Surveillance, Epidemiology, and End Results) cancer database was queried for patients treated for epithelial-myoepithelial carcinoma. The data was analyzed for patient T (tumor), N (nodal), and M (metastasis) stage, tumor site, and demographic characteristics. The Kaplan-Meier model was used to estimate actuarial survival.

Results: A total of 468 patients were identified. White patients represented 78.0% of the total. There were 291 female patients and 177 male patients. Overall 5-, 10-, and 20-year survival was 72.7%, 59.5%, and 38.3%, respectively. Mean survival time was 165.5 months. Parotid gland was the most common site with 57.7% of patients, with submandibular gland representing 9.8% of patients. Distant metastasis (M) status was unknown in 33.3%, with 2.6% being M1, 3.0% being MX, and 61.1% M0. Nodal metastasis (N) status was unknown in 33.3%, while 4.4% were N+, 4.7% were NX, and 57.5% were N0. 88.2% of patients had surgery as part or all of the treatment regimen. Univariate Kaplan-Meier analysis showed that AJCC overall stage, primary tumor (T) stage, nodal (N) stage, presence of distant metastasis (M1), age at diagnosis, race, and non-surgical treatment significantly affected survival. On multivariate analysis age, race, AJCC stage, T, N, M stage, and treatment type were significant.

Conclusions: Epithelial-myoepithelial carcinoma is a malignant, histologically biphasic neoplasm most frequently seen in the parotid gland. The nodal and distant metastasis rates are low. Age at diagnosis, race, AJCC stage, T, N, M stage, and treatment type all significantly affected survival.