Thymic papillo-tubular adenocarcinoma containing a cyst: report of a case.

We report a case of thymic papillo-tubular adenocarcinoma in a 55-year-old man, who had no symptoms. Sternotomy revealed a tumor in the anterior mediastinum, tightly adhered to the pericardium. It was resected completely. Interestingly, the tumor contained a unilocular cyst filled with mucinous fluid, suggesting that it originated from a pre-existing thymic cyst. Pathological examination of the tumor revealed a primary thymic papillo-tubular adenocarcinoma resembling a tumor of gut origin. Thymic adenocarcinomas, particularly of the tubular subtype, are extremely rare.