Adenocarcinoma arising in an intrathoracic duplication cyst of foregut origin: a case report with review of the literature.

A 41-year-old man presented with an asymptomatic superior mediastinal mass. At thoracotomy, a duplication cyst of the foregut was found. Microscopic examination of the cyst revealed mucosal alterations ranging from dysplasia and in situ carcinoma to infiltrating colonic carcinoma. Although malignant change has been reported in intra-abdominal foregut cysts, this is the first reported instance of carcinoma arising in a mediastinal duplication cyst.