[Two Cases of Stage Ⅳ Occult Breast Cancer]

The first case is a 62-year-old female who complained of painful left axillary lymph node swelling. Six months later, a CT scan revealed multiple lung nodules. Biopsies of the axillary lymph node and lung showed metastatic carcinoma from breast cancer. However, no breast tumor was found. She was diagnosed with occult breast cancer with metastasis to the axillary lymph node and lung. ER(+), PgR(±), HER2(1+). Letrozole was administered, and effective control was achieved for 20 months. The second case is a 62-year-old female who presented with back pain. A CT scan revealed left axillary lymph node swelling and multiple osteolytic changes in the thoracolumbar spine and rib. Biopsies of the axillary lymph node and thoracic spine showed metastatic carcinoma from breast cancer. However, no breast tumor was found. She was diagnosed with occult breast cancer with metastasis to the axillary lymph nodule and bone. ER(+), PgR(+), HER2(1+). Fulvestrant and denosumab were administered. However, after 6 months, she discontinued the treatment. Our results suggested that effective control could be achieved through systemic therapy and local therapy was not necessary for Stage Ⅳ occult breast cancer.