[A pathologic review of thymic neoplasms]

Pathology, particularly histology and histogenesis, of thymic neoplasms is reviewed. In this report, thymic neoplasms include thymoma, lymphoma, carcinoid and germ cell tumors (teratoma group) originating from the thymus. Ultrastructures, enzymohistochemistry and immunohistochemistry have increased the knowledge on the relation between the histogenesis, morphology and function of each neoplasm. Recently, various kinds of monoclonal antibodies have easily been available, and the use of them in immunohistochemistry is useful for differentiating the subpopulation of lymphocytes in thymomas. Some interpretations referring to the microenvironment by thymoma cells and developing T lymphocytes are described. We stressed that peanut lectin was useful for identifying cortical thymocytes in paraffin sections, and functions of S-100 protein positive cells in thymomas should be investigated for elucidating one of the questions concerning the microenvironment by thymoma cells.