Primary pulmonary mucinous adenocarcinoma is a rare subtype of lung adenocarcinoma. It differs from non-mucinous adenocarcinoma in etiology, pathogenesis, clinical, imaging, histological, immunophenotypic and genotypic features, prognosis and treatment. pulmonary mucinous adenocarcinoma mainly originates from bronchial basal cells and mucous cells. Tumor cells show a goblet and/or columnar cell morphology with abundant intracytoplasmic mucin and basally oriented nuclei, with a typical lepidic-predominant growth, the commonest molecular alterations are KRAS mutations.

Objective: To study the clinicopathological characteristics of lung salivary gland-type tumors (SGT), and to compare with the corresponding primary SGT in salivary glands. Methods: Twenty-three cases of lung SGT were retrieved from the files of Peking University First Hospital from January 2004 to September 2018. The morphology, immunophenotype, genotype and outcome of these cases were analyzed. Results: The 23 patients included 13 males and 10 females, with age range of 13-79 years (median 54 years). There were 11 cases of adenoid cystic carcinoma, 10 cases of mucoepidermoid carcinoma (MEC), one case each of clear cell carcinoma and myoepithelioma. The morphology and immunophenotype of lung SGT were very similar to their counterparts in salivary gland. MYB rearrangement was detected in one of 11 adenoid cystic carcinomas. MAML2 rearrangement was detected in all the MECs. EWSR1 rearrangement was detected in the one case of clear cell carcinoma. Of patients with adenoid cystic carcinoma, the survival time was more than 60 months (three cases), 52 months (one case), and 12-36 months (three cases). There was no recurrence and death in seven cases of MEC with follow-up results. One case of clear cell carcinoma recurred after 52 months of follow-up. Conclusions Although the SGT of lung and their counterparts in salivary gland are very similar in their morphology, immunophenotype, genotype and prognosis, there are also some differences between each other. MYB rearrangement can be detected in most adenoid cystic carcinomas of salivary gland, but rarely in lung adenoid cystic carcinoma. The prognosis of patients with lung MEC is better than that of patients with salivary gland MEC, while the prognosis of patients with lung adenoid cystic carcinoma is worse than that of patients with salivary gland adenoid cystic carcinoma.