Background: Renal cell carcinoma (RCC) is responsible for 90-95% of malignant renal neoplasms. Peak incidence is between the 5^th and 7^th decades of life. Metastatic RCC to the breast is extremely rare.

Case Report: A 55-year-old woman presented with a mass in her right breast. Mammography demonstrated a 22×32 mm mass with increased density associated with spiculation and microcalcification areas. Biopsy of the mass reported an invasive ductal carcinoma. During the evaluation of metastasis and staging, another mass (38×33×27 mm) was detected in the inferior pole of the right kidney with heterogeneous appearance. Nephrectomy was performed and the pathological evaluation of the kidney mass reported a clear cell renal carcinoma. Breast mass was vimentin-positive carcinoma that was consistent with metastasis from RCC. Breast metastasis from RCC was diagnosed and the patient treated with immunotherapy (Interferon alfa).

Conclusion: It can be concluded that the breast tissue can be a site for RCC metastasis. Therefore, after detecting a malignant breast mass, a comprehensive evaluation is necessary to differentiate between the primary and metastatic breast cancers.