Abstract
A 64-year-old woman presented with bulging of the left breast. She did not experience pain, tenderness, or abnormality of the skin. The upper left breast was obviously bulging compared with the right breast on physical examination, but the tumor could not be palpated. However, several hard and fixed lymph nodes were palpated in the left axilla. Imaging findings of the left breast revealed no abnormal findings except for numerous prominently swollen axillary lymph nodes and swelling of the left pectoral muscle. Left axillary lymph node biopsy was performed and the patient was diagnosed with metastasis of hormone receptor-positive breast cancer. Letrozole was administered, and the bulge in the pectoral muscle and the axillary lymph nodes reduced in size. Treatment has been continued for 1 year without disease progression. As occult breast cancer is rare, the standard of care is also controversial. Although many reports have recommended surgery or radiotherapy for occult breast cancer, primary systemic chemotherapy or endocrine therapy should be considered in accordance with the intrinsic subtype.
