ER-positive breast cancer recurrence with renal metastasis inside angiomyolipoma

What happened, in summary

This 67-year-old Caucasian woman presented with a right chest wall mass 19 years after a modified radical mastectomy for Stage IIB hormone receptor-positive invasive ductal carcinoma of the breast. After the original breast cancer, she had received adjuvant chemotherapy and endocrine therapy and had remained symptom-free until this new presentation. PET/CT showed a 1.8 × 1.5 cm right subpectoral lymph node with FDG uptake, suspicious for metastatic disease. The scan also found an incidental 4.1 × 3.4 cm enhancing mass in the left kidney, raising concern for renal cell carcinoma or another kidney cancer. Ultrasound-guided biopsy of the subpectoral lymph node confirmed metastatic carcinoma of breast origin, with positive staining for mammaglobulin, e-cadherin, and estrogen receptors. Because the overall burden of metastatic breast disease appeared relatively small and the kidney mass still needed diagnosis, she underwent left total nephrectomy. The kidney specimen contained a 6 cm angiomyolipoma, a benign tumor, but within it was a 2 cm focus of metastatic mammary carcinoma. The metastatic focus resembled the subpectoral lymph node biopsy and stained positive for estrogen receptor, mammaglobulin, and GCDFP-15, confirming breast origin. Surgical margins were clear, and the surrounding kidney tissue was uninvolved. She recovered well after nephrectomy and was discharged without complications. At 7-month follow-up, she continued anti-estrogen hormonal therapy and had no demonstrable progression of disease. She was offered surgery to remove the subpectoral lymph node, but she declined and continued monitoring with hormonal therapy. The kidney pathology changed the interpretation of the renal mass: it was not a separate kidney cancer, but a benign angiomyolipoma containing a small focus of metastatic breast cancer.