Case Report of Renal Cell Carcinoma Metastasis to the Breast.

Metastases from other primary malignancies to the breast are extremely rare, with an incidence of up to 2%. Renal cell carcinoma (RCC) is known to form micrometastases in unusual organs. This report describes a case of a RCC metastasis to the breast that was identified 20 years after nephrectomy. The patient, a 68-year-old female, presented after a new abnormality was found on a screening mammogram. The biopsy, which was reviewed by several pathologists, revealed a renal cell carcinoma metastasis. Imaging confirmed no other metastases, and she was treated with a partial mastectomy. This case highlights how RCC metastases can be found many years after a nephrectomy, and staining for RCC should be considered in patients with this history and a newly identified breast mass.