HD Jung, et al Fig. 3. (A) Tumor cells are positive for Leder stain and immunoperoxidase (original magnification ×400). (B) Tumor cells are negative for CD3, CD20, CD34, TdT and Pax-5 (original magnification ×40). DISCUSSION Granulocytic sarcoma is an extramedullary tumor com- posed of granulocytic precursor cells, such as myeloblast or immature myeloid cells. It is also known as myeloid sarcoma, extramedullary tumor and chloroma. Granu- locytic sarcoma clinically manifests as a solid nodular mass, which commonly affects the bone, periosteum, lymph node and skin. Granulocytic sarcomas usually occur during the course of AML and antecede blastic cirisis in myeloproliferative disease or myelodysplastic syndromes1-5. However, the tumor can also develop in patients who have either no prior history of hematological disease or have shown complete remission from acute myelogenous leukemia6-11. Aleukemic granulocytic sarco- ma is very rare. It usually precedes systemic relapse in most cases. The pathogenesis of aleukemic granulocytic sarcoma is yet to be elucidated. Takahashi et al.12 suggested that clonal evolution might be related to conversion of the character of leukemic blasts. Up-regulating expression of some adhesion molecules in the AML-M3 patient treated with all-trans retinoic acid was also hypothesized7. However, our patient had a history of AML-M1, and S272 Ann Dermatol cytogenetic analysis of the granulocytic sarcoma revealed no chromosomal abnormality with 46, XX. These facts do not fit with the above conditions. In terms of a molecular basis, the homing of T cells into the skin via interaction with integrins and endothelial-bound chemokines is suggested as a mechanism of extramedullary invasion of leukemic cells13. In the diagnosis of granulocytic sarcoma, histopathologic examination is necessary. Immunohistochemical studies of the lesions and history of underlying systemic leukemia are helpful in differential diagnosis with lymphoma, mycosis fungoides and other neoplasms. In a retrospective review, Cronin et al.14 documented that myeloperoxidase expression strongly supports the diagnosis of myeloid leukemia cutis. The treatment of aleukemic granulocytic sarcoma has not been established. Chemotherapy or radiotherapy is usually recommended. Several studies have suggested that aggressive chemotherapy at the time of diagnosis of aleukaemic granulocytic sarcoma may improve the overall survival rate and help prevent subsequent progression to AML15,16. The prognosis of aleukemic granulocytic sarcoma is poor. In such cases, relapse of leukemia occurs within a mean