ABSTRACT
Granulocytic sarcoma is a localized extramedullary solid tumor composed of immature myeloid cell and is usually associated with acute myeloid leukemia or myelodysplastic syndrome. Although it can involve any site, commonly in lymph nodes, skin, bone and soft tissue, the involvement of breast is unusual. Especially, the involvement of the breast as a pattern of relapse after bone marrow transplantation is extremely rare. We have experienced 2 cases of granulocytic sarcoma after bone marrow transplantation. One case was a 39-year-old woman with right breast mass diagnosed with granulocytic sarcoma. She had received an unrelated bone marrow transplantation due to biphenotype acute leukemia 3 years before our presentation. Another case was a 48-year-old woman with acute myeloid leukemia, who was diagnosed with granulocytic sarcoma on both breasts 8 months after allogenic bone marrow transplantation. We also discuss the clinicopathologic features of granulocytic sarcoma in breast after bone marrow transplantation.