Isolated Bone Marrow Metastasis in Metastatic Carcinoma Breast: A Rare and Unique Case

Background Bone metastasis (BM) accounts for about 65%–75% of metastatic breast cancer (MBC) cases. Unlike BM, symptomatic bone marrow metastasis (BMM) is uncommon in MBC. The reported incidence of BMM is only 0.17% in MBC and 0.6%–1.7% in other solid tumours such as gastric and lung cancer. The extent of bone marrow infiltration leading to BMM manifestations is varied and complex. Diagnosis of BMM primarily relies on bone marrow aspiration smears and biopsies. The lack of specific clinical signs in BMM makes early diagnosis challenging, underscoring the need for expertise in this field. Due to limited data in this area, the appropriate treatment of breast cancer with BMM is not extensively discussed in significant guidelines. Most patients with BMM have hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2−) tumours. The goal is to improve understanding of this disease and provide effective diagnostic and treatment strategies.