A rare case of thymoma with CA 19-9 production.

A 72-year-old man was diagnosed as having myasthenia gravis (MG). He underwent computed tomography which revealed an anterior mediastinal tumour. Laboratory examination revealed elevated levels (106.3 U/ml) of carbohydrate antigen (CA) 19-9 in serum. However, no malignant disease was detected on fluorodeoxyglucose-positron emission tomography. A diagnosis of thymoma associated with MG was considered and an extended thymectomy was performed. Histopathologically, thymoma was categorized as stage I based on the Masaoka classification, and as type AB according to the World Health Organization classification. Immunohistochemistry was positive for CA 19-9. The serum levels returned to the normal range post-operatively (16.7 U/ml). Herein, we report an extremely rare case of thymoma with raised levels of CA 19-9.