Cytological Features of Pulmonary Papillary Adenoma with Malignant Transformation and Literature Review.

Papillary adenoma of the lung is a rather rare tumor. We will present a case of papillary adenoma in the lung with malignant transformation in a 65-year-old male patient. A high dense soft tissue mass was detected in the lateral segment of the right middle lobe by CT examination. Cytologically, the tumor contained the benign cells similar to normal alveolar epithelium and the malignant cells which were significantly enlarged and irregular, crowded, or overlapping. Immunohistochemical staining showed that the epithelial cells were diffusely positive for TTF-1, napsin-A, and CK7, but were negative for p63, p40, CK5/6, CgA, Syn, CD56, and TG. The Ki67 index was about 5%. All of these evidences indicated that it was a case of papillary adenoma with malignant transformation. Thus, it should be noted that more active treatment measures should be taken to treat pulmonary papillary adenoma.