Malignant thymoma with peripheral blood lymphocytosis.

A 37-year-old woman with a giant, lymphocytic predominant thymoma involving the pleura and accompanied by a sharp peripheral blood lymphocytosis is described. Only electromicroscopic and immunohistologic studies could exclude the alternative diagnosis of mediastinal lymphoma. The tumor and peripheral blood lymphocytes were characterized as T4 lymphocytes. The thymoma responded very well to a combination of radiation and cytotoxic therapy. Forty-two months after diagnosis, the patient is still is complete remission.