Papillary adenocarcinoma developed in a thymic cyst.

In this report, we describe a case of a thymic carcinoma that developed in a thymic cyst, which was resected by video-assisted thoracic surgery (VATS). Chest radiography of a 68-year-old Japanese woman revealed an abnormal shadow. She was asymptomatic with normal physical examination findings. Chest computed tomography demonstrated a well-confined cystic mass that measured 4 cm in diameter occupying the anterior mediastinum. Based on these findings, a thymic cyst was suspected. It was completely resected by VATS. The excised cyst was multiloculated with a partially thick wall. Microscopic examination revealed that the nodular excrescence of the wall to be limited to papillary adenocarcinoma and the cyst wall to be lined by cuboidal cells. On the basis of this diagnosis, we performed multidrug adjuvant chemotherapy. The patient was alive without any sign of recurrence 15 months after the operation.