[Ciliated Muconodular Papillary Tumor of the Lung].

A ciliated muconodular papillary tumor (CMPT) has been reported to be a low-grade malignant tumor or benign tumor, consisting of ciliated columnar cells and goblet cells with basaloid cell proliferation, occur in the peripheral lung. We present a case of CMPT in this report. A 42-year-old male was referred to our department due to a nodule detected in the peripheral left lower lobe of lung. The nodule was resected via wedge resection based on a suspected diagnosis of carcinoma. Intraoperative analysis of the frozen sections was suggestive of mucinous adenocarcinoma. A left lower lobectomy and mediastinal lymph node dissection were performed. The resected specimen was characterized as a papillary tumor with central fibrosis, proliferating along the alveolar walls, surrounded by mucous lakes, and consisting of ciliated columnar cells and goblet cells. Nuclear atypia was mild, and no mitotic activity was observed. Based on these findings, the tumor was finally diagnosed as CMPT. No recurrence has been noted for 24 months after surgery.