[A case of mediastinal mature teratoma presenting increased serum CA19-9 level].

A case of mediastinal mature teratoma with elevated serum CA19-9 level is reported. A 50-year-old woman admitted to our hospital complaining of cough and chest pain. Chest X-ray showed an abnormal mass shadow with retention of the right pleural effusion. Her serum CA19-9 level was high (204.4 U/ml), while serum AFP, CEA, HCG levels were normal. On lateral thoracotomy, an anterior mediastinal tumor perforating into the right lung was revealed and the total resection of the tumor with adherent part of the right lung was performed. Postoperatively, her serum CA19-9 level returned to normal. Histological examination disclosed a mature teratoma consisting of skin, pancreatic tissue, cartilage, bronchial epithelium, etc. Immunohistochemical staining were positive in the bronchial epithelium and bronchial gland but was negative in the pancreatic tissue of the tumor. This is a rare case of mediastinal mature teratoma with elevated serum CA19-9 level and negative immunohistochemical staining for it in the pancreatic tissue of the tumor.