Histopathological changes in invasive thymoma in patients with recurrence.

In the last 20 years, we treated 123 cases of thymoma. In 2 patients histopathological features of the tumors changed during the long-term follow up. In one patient the tumor was resected along with the invaded tissues. Eleven years later, recurring tumor and the invaded organs were extirpated. Hepatic metastasis was detected by abdominal CT scanning 16 years after the first operation. Two years later she died in an accident. Histopathologically, the primary thymoma was lymphoepithelial type and the recurrent tumor was epithelial type. In the other patient, four years after the surgical treatment for thymoma with disseminated lesions, recurrent disseminations were removed. Eight years later, both the disseminated and a metastatic lesion were resected. This patient is currently well without tumor 14 years after initial detection of the disease. Both the primary and recurrent thymoma were lymphoepithelial type and the third tumor was epithelial type. Thus, slow-growing thymomas in patients with long-term survival possibly undergo histological change.