Pulmonary Inverted Schneiderian Papilloma Causing High Serum Levels of Carcinoembryonic Antigen and Squamous Cell Carcinoma-Associated Antigen: Report of a Case

We report a rare case of inverted Schneiderian papilloma causing exceedingly high serum levels of carcinoembryonic antigen (CEA) and squamous cell carcinoma-associated antigen (SCC). A 74-year-old man presented with a 6-month history of a productive cough, bloody sputa, and dyspnea. Chest computed tomography showed massive infiltration in the lower lobe with multiple focal soft tissue densities. Blood biochemical analysis revealed a serum CEA level of 107.0 ng/ml (normal <5.0 ng/ml), and an SCC level of 373.0 ng/ml (normal <1.5 ng/ml). Squamous papilloma was diagnosed by histological examination of a bronchoscopic biopsy specimen. To alleviate the patient's symptoms and refine the diagnosis, we performed a right lower lobectomy. The lower lobe of the lung was filled with mucinous sputa and very fragile papillary tumors of various sizes. Microscopic examination revealed papillary growth of stratified epithelial cells with massive mucin production. No nuclear abnormality or invasion of the basal membrane of the tumor cells was observed. Postoperatively, the patient's symptoms resolved quickly, and the serum levels of CEA and SCC decreased to 6.4 ng/ml and 1.7 ng/ml, respectively, within 3 months.