[Lymphocytic thymoma developing in the wall of a thymus cyst]

Among 648 patients having undergone thymectomy for myasthenia, the authors observed one female in which the operation revealed a multilobular cyst of the thymus. The features of the histological structure of the cyst undoubtedly indicate its primary nature. A detailed microscopic examination of the fibrous cyst wall revealed some elements of the tumor growth having the structure of lymphocytic thymoma. In the authors' opinion, the fact of the development of thymoma in the cyst wall is an additional argument in favour of early surgical treatment of patients with myasthenia, particularly in the presence of cyst degeneration of the thymus.