Extrathymic malignancy in patients with myasthenia gravis.

The presence of extrathymic malignancies was investigated in 296 thymectomised myasthenia gravis (MG) cases. In 5 of the 296 cases, extrathymic malignant tumours were observed. 4 of the 5 cases had thymomatous MG. 3 cases had malignant fibrous histiocytoma. Extrathymic malignancies were observed more frequently in thymomatous MG than in non-thymomatous MG. 59 cases (60 tumours), including our 5 cases, who had MG and extrathymic malignant tumours were compiled from the literature. In the 60 extrathymic malignancies, leukaemia and reticulo-endothelial sarcoma were the most frequent types.