T-cell lymphoblastic leukemia/lymphoma presenting in a recurrent thymoma.

A lymphoblastic malignancy presented as the lymphoid component of a recurrent invasive lymphocyte-rich thymoma that had been previously resected and treated with chemotherapy. This high grade lymphoid neoplasm concurrently involved mediastinal nodes and subsequently disseminated to pleural fluid and peripheral blood. Lymphocytes with convoluted nuclei demonstrated a T-lymphoblastic phenotype (UCHL1+, Leu-22+, TdT+) by immunohistochemical studies. T-cell lymphoblastic leukemia/lymphomas in this clinical setting have not been reported, and this case suggests that neoplastic transformation of lymphocytes may occur in longstanding refractory thymomas.