Central papillary adenoma of the lung diagnosed in a bronchoscopy-guided FNA: Cytological and histological characterization of this rare entity.

Pulmonary papillary adenoma (PA) is an unusual tumor with only 32 reported cases to date. We present a case of a 69-year-old man, a smoker from the age of 12, with a central mass in the pulmonary left lower lobe identified in a PET-CT scan. Microscopical analysis of the Fine Needle Aspiration (FNA) samples showed fragments of a tumor comprised of abundant papillary structures lined by a monolayer of cytologically bland columnar to cuboidal epithelial cells. The immunohistochemical stains were positive for CK7, TTF-1 and EMA in the epithelial cells, and negative for MYC. Based on the imaging tests, histological features and immunohistochemical profile, the tumor was diagnosed as pulmonary PA. The cytologic and histologic features of this rare entity are described in detail and the value of FNA as an essential presurgical diagnostic procedure is emphasized.