Diffuse Bone Marrow Metastasis as the Initial Presentation of anOccult Breast Cancer

Breast cancer is one of the malignancies which tend to involve the bone marrow, but initial presentation with diffusebone marrow metastasis from an occult breast cancer is very rare. Prognosis is generally very poor for marrow metastasis from solidtumors except that breast cancer is a treatable disease even in such a dismal condition.Case. A 64-year-old woman’s headache wasfound to result from diffuse adenocarcinoma metastasis in the bone marrow from an unknown primary site. Intensiveimmunohistochemistry study of bone marrow biopsy specimen confirmed the disease nature to be an estrogen receptor-positive/human epidermal growth factor receptor 2-negative breast cancer. Mammography and magnetic resonance imaging ofbreasts revealed a suspicious primary lesion in the right breast. Treatment with tamoxifen alone achieved a sustained response.Discussion. Mucin 1 (MUC1), also known as cancer antigen 15-3 (CA 15-3), facilitates motility and metastatic potential ofbreast cancer cells. Interleukin-1β(IL-1β) drives breast cancer cell growth and colonization in bone marrow adipose tissueniche. Receptor activator of nuclear factor kappa-B (RANK) and its ligand (RANKL) activate osteoclasts to make a favorablebone marrow microenvironment for tumor cells. Agents against MUC1, IL-1β, and RANKL might be of therapeutic effect forpatients like ours