[Thymoma--clinical aspects and its biological function].

Thymoma is a neoplasm of thymic epithelial cells. The tumor grows relatively slowly, and the prognosis is very good after surgical resection. However, therapy for advanced thymoma has not been established, and the effect of modern chemotherapy is being evaluated. Thymoma is unique in that 25-30% of the patients have associated myasthenia gravis with autoantibodies to acetycholine receptor. The malignant epithelial cells maintain the function of cortical epithelial cells and harbor non-neoplastic immature T cells of CD 3(low) CD 4(+)CD 8(+) phenotype. This function has a causative relationship with the associated myasthenia gravis. Also, the presence of CD 3(low) CD 4(+)CD 8(+) T cells is diagnostic of thymoma and can be utilized for rapid diagnosis using needle biopsy specimen.