TESTICULAR EXTRAMEDULLARY MYELOID CELL TUMOR IN A PATIENT WITH MYELODYSPLASTIC SYNDROME

We report herein a case of extramedullary myeloid tumor arising bilate rally in the testes of a 66-year-old man, who had previously been diag nosed with myelodysplastic syndrome. Light microscopy of the testicula r neoplasm demonstrated a tumor composed of large, slightly polygonal cells with pale blue to weakly eosinophilic cytoplasm. The tumor cells were immunoreactive for CD45, myeloperoxidase, lysozyme, CD43, and MB 2. Many of the cells also expressed chloroacetate esterase. Peripheral blood and bone marrow findings were consistent with chronic myelomono cytic leukemia (FAB-CMML), particularly in the most recent material, w hich showed clear cellular dysplasia and an increase in the percentage of blasts in the bone marrow (15% to 20% of all nucleated cells). Thi s case of extramedullary myeloid tumor is unusual in view of the patie nt's age and the testicular location. It emphasizes the importance of including extramedullary myeloid tumor in the differential diagnosis o f histologically undifferentiated large-cell tumors, as well as a need to use a broad panel of immunohistochemical stains in such cases.