Solitary peripheral pulmonary papilloma evaluation on frozen section: a potential pitfall for the pathologist.

Endobronchial papilloma is a rare entity that is in the differential for solitary pulmonary nodule. It almost always follows a benign course, with only rare malignant transformation being reported in the squamous variant. No malignant transformation of the glandular variant has been reported to the best of our knowledge, and therefore endobronchial papilloma must be distinguished from more aggressive neoplasms. This distinction is particularly important when one encounters this neoplasm in a peripheral location at frozen section. We report a case of a 65-year-old female with an incidentally discovered solitary peripheral pulmonary nodule identified during a commercial whole-body screening computed tomography (CT) scan. Interval scans revealed a concerning doubling time, and she presented to the surgical service for removal of the mass. Intraoperative frozen section evaluation revealed histologic characteristics favoring a benign neoplasm. Permanent histologic section revealed a glandular papilloma. Over 7 years of follow-up revealed a benign clinical course.