Outcome of Primary Lung Salivary Gland-Type Carcinoma: A Population-Based Study

Introduction. Primary pulmonary salivary gland-type carcinomas are rare malignancies arising from minor salivary gland tissue in the lower respiratory tract. Given their rarity, constituting <1% of all primary lung malignancies, their epidemiological features and outcomes remain poorly documented. This study analyzed data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database to identify primary pulmonary salivary gland carcinomas, including the most prevalent tumor types. Methods. All patients diagnosed with mucoepidermoid carcinoma, adenoid cystic carcinoma, and epithelial-myoepithelial carcinoma, with the lung designated as the primary site between 1975 and 2019, were subject to analysis. Overall and disease-specific survival were calculated using Kaplan-Meier curves and Cox proportional hazards models. Results. The study identified 323 mucoepidermoid carcinoma, 284 adenoid cystic carcinoma, and 6 epithelial-myoepithelial carcinoma diagnosed as pulmonary salivary gland-type carcinoma. An analysis of age distribution revealed a unimodal pattern for both mucoepidermoid carcinoma and adenoid cystic carcinoma, with most patients diagnosed after age 40. Most patients were Caucasians (77% for mucoepidermoid carcinoma and 83% for adenoid cystic carcinoma). Both disease-specific and overall survival were worse for patients diagnosed at the age of 60 years or above. Race or sex did not significantly impact patient survival. High-grade mucoepidermoid carcinoma demonstrated a significantly worse prognosis than low or intermediate-grade mucoepidermoid carcinoma. Conclusion. A comprehensive review of clinical and epidemiological features of pulmonary salivary gland-type carcinomas reveals that the age of diagnosis and tumor grade are the most significant factors in determining patient survival.