RESUMEN
<p><b>OBJECTIVE</b>To study the clinicopathologic characteristics of primary salivary gland-type lung carcinomas, and the immunophenotypic value of TTF-1, Napsin A and Ki-67 in their differential diagnosis.</p><p><b>METHODS</b>Totally 48 special type lung cancer surgical removal specimens were collected in China-Japan Friendship Hospital during September 2009 to December 2014. A panel of immunohistochemical markers (TTF-1, Napsin A, Ki-67, CK5/6, CK7 and p63) were conducted on these specimens.</p><p><b>RESULTS</b>The 48 cases of special type lung cancer included 25 cases of primary salivary gland-type lung carcinoma (18 cases of adenoid cystic carcinoma and 7 cases of mucoepidermoid carcinoma), 5 cases pulmonary adenocarcinoma with mucoepidermoid carcinoma-like or adenoid cystic carcinoma-like structure, and 18 cases of pulmonary adenosquamous carcinoma. Compared with pulmonary adenocarcinoma with mucoepidermoid carcinoma-like or adenoid cystic carcinoma-like structure and pulmonary adenosquamous carcinoma, primary salivary gland-type lung carcinomas have special characteristics in median age, sex, location, tumor size, LN involvement and pleura invasion, with negative TTF-1 and Napsin A expression as well as lower Ki-67 index detected by immunohistochemistry. Primary salivary gland-type lung carcinomas usually have an indolent behavior.</p><p><b>CONCLUSIONS</b>Primary salivary gland-type lung carcinomas are low-aggressive entities. The origins of primary salivary gland-type lung carcinomas were different from that of pulmonary adenocarcinoma with mucoepidermoid carcinoma-like or adenoid cystic carcinoma-like structure and pulmonary adenosquamous carcinoma. Negative TTF-1 and Napsin A expression as well as Ki-67 index lower than 20% have special value for primary salivary gland-type lung carcinomas in their differential diagnosis.</p>