Superior mediastinal mature cystic teratoma with gastrointestinal adenocarcinoma transformation: Report of a case

Presented herein is a case of mediastinal mature teratoma with adenocarcinomatous transformation predominantly composed of mucinous adenocarcinoma in a 25-year-old man. Disease progressed despite application of surgical removal, adjuvant radio- and chemotherapy. Further immunohistochemical stains indicated a gastrointestinal origin of the tumor. Consequently chemotherapy according to the FOLFIRI regimen was applied that resulted in good response. To our knowledge, this is the first report of a clinical remission from chemotherapy with the FOLFIRI regimen after comprehensive initial treatment with surgery, radio- and chemotherapy for a patient with teratoma with malignant transformation, highlighting the importance of choosing an appropriate chemotherapy regimen.