Case Report: Bone Marrow Infiltration with Anemia and Thrombocytopenia, Rare Initial Symptoms of Breast Cancer.

Introduction: Bone metastasis is common in breast cancer, causing pain, myelosuppression, and hypercalcemia. However, bone marrow invasion leading to pancytopenia is exceedingly rare, and its optimal treatment remains a subject of debate. This report presents the first such case from Vietnam, where chemotherapy proved effective. Case Presentation: A 47-year-old female patient presented to the emergency department with cough, dyspnea, and back pain. Initial laboratory tests revealed WBC 21.83 G/L, neutrophil 10.97 G/L, Hct 27.3%, Hgb 87 g/L, and PLT 22 G/L. Further examination identified a left breast tumor with skin invasion, as well as metastases to the bone, liver, lungs, pleura, cervical lymph nodes, and mediastinal lymph nodes. Bone marrow aspiration confirmed the presence of malignant cell invasion. The patient responded well to chemotherapy with doxorubicin and cyclophosphamide, with platelet counts recovering immediately after the first cycle. Conclusion: Bone marrow infiltration causing pancytopenia is a rare but serious manifestation of metastatic breast cancer. Management should follow general principles for metastatic breast cancer. Chemotherapy can be considered when rapid disease control is needed or in patients with marrow failure, provided that doses are individualized and treatment is closely monitored. Further data are required to better define optimal therapy in this setting.