The patient proceeded to ultrasound-guided core biopsy of this mass.

MICROSCOPIC DESCRIPTION: Sections of breast core biopsies show features of metastatic renal cell carcinoma of clear cell type. The tumour is comprised of nests surrounded by delicate vascular stroma.

DIAGNOSIS: Right breast 1 o'clock 4 cm biopsy: Metastatic carcinoma features in keeping with a renal primary. SUPPLEMENTRAY REPORT Immunohistochemistry on core biopsy shows tumour cells stain positive with CD10 and negative with ER. Features support the diagnosis of metastatic renal cell carcinoma.