Thymoma in an Older Woman Presenting as Bowel Obstruction

Thymomas are slow growing and rare tumors (<1% of all cancers) most commonly seen in the anterior mediastinum. These are often discovered incidentally on imaging and may cause clinical symptoms of myasthenia in up to 50% of the cases. Although thymomas can metastasize to the bowel, direct extension is extremely rare and only described in a few case reports. We present a case of a mediastinal thymoma extending into the abdomen and causing symptoms of partial bowel obstruction in an older woman who then had an excellent clinical response to proton beam radiation, contrary to the anticipated course.