Pulmonary papillary adenoma presenting in central portion: a case report

Pulmonary papillary adenoma is a very rare tumor usually presenting in periphery of the lung. Herein, we present a case of pulmonary papillary adenoma located in central portion of the lung in a 17 year-old Chinese female. A well-defined mass was incidentally detected at right pulmonary hilar region by imaging examination. Histologically, the tumor is predominantly composed of abundant papillary structures lined by columnar to cuboidal epithelial cells resembling type II pneumocytes. Immunohistochemical staining showed that the epithelial cells were diffusely positive for cytokeratin, cytokeratin7, TTF-1, EMA, surfactant apoprotein A, Napsin A, P63 and β-catenin. The Ki-67 proliferation index was approximately 2 %. Based on morphologic features and the immunohistochemical profile, the tumor was consistent with pulmonary papillary adenoma. Thus, it should be noted that pulmonary papillary adenoma was also a possible diagnosis for a central mass.