Solitary breast mass as initial presentation of clinically silent metastatic renal cell carcinoma

Metastasis to the breast from extramammary tumors is rare. Breast metastases of renal cell carcinoma (RCC) origin have been described in sporadic case reports. We present a patient with a solitary breast mass representing the manifestation of clinically silent, metastatic RCC. A 76-year-old female was 12 years prior removed from radical nephrectomy for localized RCC. Her new breast mass was identified on physical examination. Pathology of the resected mass was diagnostic of metastatic RCC and subsequent imaging studies demonstrated a 1.9 cm renal mass in her solitary kidney. The patient elected subcutaneous Interleukin-2 immunotherapy as primary treatment for her recurrent RCC.