Myeloid sarcoma involving the breast.

Myeloid sarcoma is a tumor mass with extramedullary growth pattern, composed of myeloblasts or immature myeloid cells. The development of myeloid sarcoma may precede or concur with acute or chronic myeloid leukemia (AML or CML) or other myeloproliferative diseases or myelodysplastic syndromes (MDS). Isolated myeloid sarcoma of the breast is very rare. A case is presented of a 25-year-old, previously healthy woman that presented to our department for a palpable node, 5 x 2 cm in size, in the upper medial quadrant of her left breast. Fine needle aspiration (FNA) produced a sample consisting of medium sized blasts. Additional work-up revealed anemia, thrombocytopenia and leukocytosis, along with atypical blasts detected in peripheral blood and bone marrow smear. Based on the morphology, cytochemical characteristics and immature cell immunophenotype, it was considered a case of acute myeloid leukemia without maturation. In spite of intensive chemotherapy, the patient died within a year of diagnosis. In cases of isolated breast myeloid sarcoma, the diagnosis can be missed if the possibility of myeloid sarcoma is not remembered on differential diagnosis of a breast neoplasm.