Cortical versus medullary thymomas: A useful morphologic distinction?

We have tested the hypothesis that thymomas can be classified solely on the basis of epithelial cell morphology and that this distinction is prognostically useful. One hundred thymic epithelial tumors were classified according to the morphologic resem-blance to cortical or medullary thymic epithelium and to the traditional classification (lymphocytic, epithelial, mixed, and spindled). Follow-up data was obtained on 78 patients. Fifty-eight percent of the tumors were invasive. Nineteen of the invasive tumors relapsed and none of the non-invasive tumors relapsed ( P