Superior mediastinal teratoma containing well-differentiated bowel.

A previously fit and well 14-month-old-girl presented with a 2-month history of worsening cough and wheeze. Chest radiograph revealed a widened mediastinum and thoracic CT showed a large mixed density mass in the superior mediastinum, consistent with a mediastinal teratoma. Her tumor markers were within the normal range. The mass was resected and found to be a mature cystic teratoma. Surprisingly, well-formed bowel-like structures were present, containing all bowel wall layers and having a ganglionated myenteric plexus. The identification of complete sections of bowel in this context is a rare finding and to the best of our knowledge has not been published previously for the mediastinal teratoma. The possibility of secondary neoplasia developing in these areas is a complicating factor.