Myeloid sarcoma is a rare presentation of acute leukemia as a solid tumor at various extramedullary sites. It may present concurrently, before or after the onset of systemic bone marrow leukemia. Unusual clinical localization may lead to misdiagnosis, or delayed diagnosis and treatment. We describe the first case, to our knowledge, of de novo myeloid sarcoma of the breast confirmed as acute promyelocytic leukemia. Immunohistochemical analysis, flow cytometry, fluorescent in situ hybridization analysis and molecular analysis using RQ-PCR of tissue samples should be routine in determining the correct diagnosis in this setting.

Background: Leptomeningeal metastasis (LM) in breast cancer is associated with a poor prognosis. Although no randomised trial has demonstrated that intrathecal chemotherapy actually prolongs survival, this treatment is considered standard of care in this setting. The prognosis of patients with LM is poor, with a median overall survival time of less than 6 months. Methods: Herein, we report a case of a young woman with breast cancer who presented with LM at the time of relapse and was subsequently treated with two lines of intrathecal chemotherapy that prolonged survival. Results: A 28-year old woman without a significant past medical history was diagnosed with triple-negative invasive ductal carcinoma. Eight months after adjuvant treatment she developed multiple brain metastases and LM developed subsequently 1 month after finishing whole brain irradiation. Initially, she was treated with a combination of methotrexate, cytarabine and dexamethasone intrathecally but after 3 months she presented with a worsening clinical status and increased numbers of cancer cells in cerebrospinal fluid. Subsequently, she received a combination of thiotepa and methotrexate intrathecally, which resulted in a prolonged response lasting 10 months. The patient died 32 months after initial diagnosis and 18 months from LM infiltration due to disease progression in the liver and lungs as well as LM. Conclusion: The prognosis of patients with LM remains poor because of the limited effectiveness of currently available therapies; however, intrathecal chemotherapy could substantially prolong survival in selected patients.