A Case of Cystic Thymoma with Extensive Necrosis Detected in an Asymptomatic Patient

Abstract

A 53-year-old woman was referred to our department with a mediastinal tumor measuring 70×50 mm incidentally identified on a chest computed tomography. The mass primarily consisted of fluid and contrast enhancement was observed in part of its wall, which was consistent with a thymoma or a teratoma. We planned to resect it. A tense cystic mass was arising from the right lobe of the thymus. Only a small portion of the adhered right mediastinal pleura was concomitantly resected, resulting in complete tumor resection. On incision of the capsule, dark brown components were discharged, and necrotic tissue was deposited at the bottom. Pathological examination revealed that the cyst contents consisted mainly of necrotic tissue. In solid white areas in the cyst wall, we identified AE1/AE3-positive epithelial components and terminal deoxynucleotidyl transferase-positive lymphocytes. Therefore, it was diagnosed as Type AB (WHO classification), T1N0M0-Stage I (UICC-TNM classification), and Stage I (Masaoka classification) thymoma. Thymomas present with various pathologic pictures such as cystic changes and necrosis. We report a relatively rare case of asymptomatic cystic thymoma even with extensive necrosis.