Case Report: Difficulties in diagnosis of myeloid sarcoma of the breast by core needle biopsy.

Background: Myeloid sarcoma (MS) is a rare neoplasm that arises from myeloid blasts outside the bone marrow. Diagnosing and treating MS in the breast can be challenging due to its rarity in this location. Clinicians should consider MS when a breast mass is detected to implement appropriate treatment and avoid unnecessary surgery. Case demonstration: A 25-year-old female with a 2-year history of acute myeloid leukemia and a 1-year history of hematopoietic stem cell transplantation was admitted due to bilateral breast masses present for 1 month. Breast MRI plain scan + enhancement revealed bilateral breast masses with irregular shapes, irregular borders, and significant enhancement, suggesting a malignant tumor. A bilateral breast biopsy was performed, and the pathological diagnosis confirmed MS involving the breast. Following the diagnosis, local radiotherapy was performed, and no recurrence was observed during the 1-month follow-up. Conclusion: The clinical manifestations of MS in the breast are typically nonspecific, and its imaging features resemble those of breast cancer or other malignant tumors. Therefore, diagnosing primary MS of the breast without a history of leukemia is challenging, and the final diagnosis requires a histopathological biopsy. For patients with a history of AML, imaging should be regularly reviewed for early detection, diagnosis, and treatment to improve prognosis.