Abstract
BACKGROUND: Renal cell carcinoma most commonly metastasizes to the lungs, skeleton or liver. Metastatic renal cell carcinoma to the breast is very rare, especially for clear cell carcinoma, and few cases regarding this condition have been reported. CASE PRESENTATION: The case we presented was a 68-year-old Chinese female with metastatic renal clear cell carcinoma of the left breast 10 years after a nephrectomy. Identification of the metastatic renal clear cell carcinoma in the breast required multiple breast imaging modalities. Imaging showed a single, ovary-shaped, well-defined hypo-echoic mass, with abundant blood flow on ultrasound images. The mass was enhanced early on MRI, and it was hypointense on a T1-weighted image and hyperintense on a fat-saturated T2-weighted image. Following surgical excision of the tumor, a routine immunohistochemistry antibody panel on the tumor cells revealed negative staining for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (Her-2). Strong positive staining for the cluster of differentiation 10 (CD10) and vimentin was present. CONCLUSION: This case is unusual because of the site of metastatic progression. It is important for physicians to be aware of this progression so early diagnoses can be made, and appropriate therapeutic planning can be initiated.