Bone marrow metastasis is very uncommon in breast cancer. Cancer patients showing a dramatic response to chemotherapy with full recovery are very rare.

This is a case report of a 62-year-old woman who underwent partial mastectomy six years previously. The patient presented with increased fatigue and her hemoglobin level was 6.7 g/dl. Pathological examination of a bone marrow biopsy showed metastasis from breast cancer. Systemic therapy was initiated with doxorubicin and cyclophosphamide and pancytopenia was steadily improved. However, 15 months later, she felt severe fatigue again. Eribulin was administered and the patient showed sufficient recovery. She had two bone marrow metastases that caused pancytopenia including severe anemia. However, she survived twice with chemotherapy.

Bone marrow metastasis of breast cancer is life-threatening; however, chemotherapy may significantly improve survival.