Objective To analyze the disease spectrum and prognosis of each pathological subtype of rare lung malignancies.

Methods We retrospectively analyzed the clinical data of rare primary lung malignancies diagnosed pathologically from 2004 to 2015 in the SEER database, as well as the composition and incidence trend of each subtype. Kaplan-Meier method was used to calculate the 1-, 3- and 5-year survival rates and draw the survival curves.

Results We included 13428 patients totally, including large cell carcinoma, adenosquamous carcinoma, sarcomatoid carcinomas, salivary gland-type tumor, lympho-epithelial carcinoma, mesenchymal tumors and tumors of ectopic origin; and their composition ratios in all lung malignancies in the same period were 1.72%, 1.13%, 0.36%, 0.09%, 0.01%, 0.19% and 0.01%, respectively. The composition ratio of large cell carcinoma decreased year by year, while that of adenosquamous carcinoma increased slowly. The 5-year overall survival rate of all patients with rare lung malignancy was 16.86% and the median survival time was 8 months.

Conclusion Adenosquamous carcinoma of the lung has become the first rare primary malignant lung tumor in the sequence of incidence. Rare primary malignant tumors in the lung have poor overall prognosis because the driving gene mutation rate is low and rare mutation type is common.