Abstract
BACKGROUND: Myeloid sarcoma (MS) is a rare extramedullary tumor composed of immature myeloid cells, most commonly associated with acute myeloid leukemia (AML). Although it typically occurs in the skin, lymph nodes, bone, and soft tissue, breast involvement is extremely uncommon and may mimic breast carcinoma or lymphoma. CASE REPORT: A 34-year-old woman presented with a left breast mass initially suspected to be carcinoma. Histopathological and immunohistochemical analyses confirmed myeloid sarcoma, with no evidence of systemic involvement. The patient achieved complete remission after AML-based induction chemotherapy followed by allogeneic stem cell transplantation and remains in remission at one year of follow-up. CONCLUSION: Breast MS is a rare and diagnostically challenging entity. Accurate immunohistochemical evaluation is crucial to avoid misdiagnosis and treatment delay. AML-oriented systemic chemotherapy, and allogeneic stem cell transplantation when appropriate, remain the most effective strategies to achieve long-term remission.