Stage 4 luminal A breast cancer: tumor regression on hormone therapy

What happened, in summary

A 42-year-old woman had been treated for left-sided breast cancer 10 years earlier with lumpectomy, adjuvant chemotherapy, radiotherapy, and 5 years of hormonal therapy. Her original stage was not reported. She later presented with several enlarging soft-tissue masses on the right lower back, both thighs, and the back of the neck. The neck and back lesions were fluctuant, warm, and tender, and the back mass had serous discharge. She also reported weight loss, decreased appetite, and subjective fever. Examination found a 4 x 8 cm posterior neck mass, an approximately 8 x 10 cm lower-back mass, small bilateral thigh masses, and a 2 x 2 cm firm mobile mass in the right breast. Infection was considered, but cultures and serologic testing were negative. CT imaging showed a large posterior neck subcutaneous lesion, an 8 cm lower chest/upper abdominal wall subcutaneous mass, a left upper-lobe lung lesion attached to the pleura, a 1 cm left hilar node, and small bilateral pulmonary nodules. Fine-needle aspiration of the neck mass showed atypical cells, and biopsy of the thick cavity wall confirmed metastatic mammary ductal carcinoma. The tumor was ER-positive in 91-100% of cells, PR-positive in 71-80%, and HER2-negative, consistent with Luminal A disease. Biopsy of the lung lesion also supported metastatic breast cancer. Staging showed no abdominal or pelvic metastases, but the skin/soft-tissue and lung involvement made this Stage IV recurrent breast cancer. After Breast Tumor Board review, she started anti-hormone therapy plus capecitabine. At 3 months, the tumors were regressing and lung metastasis was stable.