|| Worldwide, breast cancer accounts for 22.9% of all cancers excluding non-melanoma skin cancers in women. More than 80% of breast cancer cases are discovered when a woman discovers a lump that feels different from the rest of the breast tissue. We report the case of a 60-year-old woman who had been treated for one year at a psychiatric hospital for suspected schizophrenia, and was referred to our hospital on March 23, 2011 for consultation regarding complete blood count abnormalities: hemoglobin, 4.8g/㎗ ; Plt, 1.9×104/μl ; WBC, 12,700/μl with 18.5% abnormal cells. Computed tomography revealed an enhanced, irregular mass in her right breast as well as right axillary lymph node swelling, suggestive of breast cancer. BM biopsy confirmed the presence of abnormal, keratin-positive cells, suggesting metastasis to the bone. CA15-3 was 300U/㎖ (normal range ＜25). The patient died on April 11, 2011, post-admission day 20. We found a rare case of terminal breast cancer that presented with peripheral blood abnormality. Breast cancer in patients who do not notice breast abnormality can present with peripheral blood abnormality.