Primary salivary gland-type tumors of the lung: A systematic review and pooled analysis

Introduction: Primary salivary gland-type tumors of the lung (PSGTTL) are rare intrathoracic malignant neoplasms. Their description in literature is largely limited to a few case series and case reports. A systematic review and pooled analysis of the previously reported cases of PSGTTL is presented here. Methods: Electronic database of PubMed using keywords "lung neoplasm" AND "salivary gland tumors" was used to identify the papers documenting the PSGTTL. Filters (publication date from January 1, 1900--December 31, 2015, Humans and English) were applied to refine the search. A pooled analysis of clinical, pathological, treatment, and survival data was performed. Results: The present systematic review included 5 studies and a total of 233 patients. Mean age of the patients was 41 years (range 6-80 years) and there was a male preponderance (1.3:1). Common pathological types were mucoepidermoid (MEC) (56.6%), adenoid cystic (ACC) (39.5%), and epithelial-myoepithelial cancer (3.8%). Tumors were located in the central airways (trachea and major bronchi) in 43.3% of patients. Weighted median tumor size was 4.2 cm. Surgery was the primary treatment undertaken in 82.4% of the patients, while radiotherapy and chemotherapy were also used in 15.9% and 9.4% of the patients. Lymph node involvement was seen in 15.2% of the patients. Disease recurrences were observed in 21.1% of the patients (12.9% and 37.5% in MEC and ACC, respectively). Three-, 5-, and 10-year weighted overall survival was 86.4%, 81.4%, and 73.6% (93.8%, 90.0%, and 85.0%, respectively, for MEC and 76.7%, 62.8%, and 50.5%, respectively, for ACC). Conclusion: Surgery is the primary treatment of PSGTTL to achieve long-term survival. Role of chemotherapy and radiotherapy in the management of PSGTTL warrants further studies.