[A Case of Renal Cell Carcinoma with Solitary Mammary Metastasis 28 Years after Surgery].

Metastatic breast tumors account for 0.5-2.0% of all malignant breast tumors; however, metastasis of renal cell carcinoma to the breast is extremely rare. Here, we report a case in which an isolated breast metastasis was found 28 years after total nephrectomy for renal cell carcinoma and resection was performed. The patient was a 52-year-old woman who had undergone right radical nephrectomy for right clear cell renal cell carcinoma at the age of 24 years. Twenty-eight years after the surgery, she noticed a mass in her right breast and visited a local hospital. Ultrasonography revealed a breast mass, sized approximately 1.5 cm, in the right C region; therefore, a needle biopsy was performed for a qualitative diagnosis. Histopathological findings were similar to those of primary renal cell carcinoma, and breast metastasis of renal cell carcinoma was considered. PET-CT did not reveal accumulation in other organs; therefore, the diagnosis was isolated breast metastasis, and surgical resection was decided. Right partial mastectomy was performed, and a histopathological examination of the resected specimen led to the diagnosis of metastatic renal cell carcinoma.