Renal Cell Carcinoma Presenting as a Solitary Breast Mass. A Diagnostic Pitfall on Aspiration Cytology of Clear Cell Tumors of the Breast

Abstract

A 65-year-old female presented to her oncologist after noticing an enlarging, solitary painless rightsided breast mass. Eight years previously, she had undergone right radical nephrectomy for a renal clear cell carcinoma. On examination, a soft retroareolar mass without skin or nipple changes was noted. Mammography revealed a solid smooth nodule in the mid portion of the right breast not seen on her previous mammograms 1 year prior ( Fig. 1). Ultrasound confirmed a 2.2-cm round, hypo-echoic nodule with welldefined margins and no shadowing (Fig. 2). Fine needle aspiration (FNA) biopsy and immunocytochemical study were performed.The aspiration was cellular mostly at the edges of the smears. The cells formed papillary, loose small clusters as well as isolated single cells (Fig. 3a,b). The individual cells were round to oval with moderate to abundant cytoplasm and essentially centrally or eccentric nuclei. The cytoplasm was foamy. The nuclei showed mild pleomorphism, but the nuclear ⁄ cytoplasmic ratio was not increased. Immunocytochemistry with monoclonal antibody to pancytokeratin (Novocastra, 5D3, prediluted, Novocastra, Newcastle, UK) and vimentin (Novocastra, V9, prediluted), which showed dual positivity and was against a breast primary. Cell block preparation showed aggregates of clear cells with clear cytoplasm and eccentric nuclei. Figure 1. Mammography revealed a solid smooth nodule in the mid portion of the right breast.Figure 2. Ultrasound confirmed a 2.2 cm round, hypo-echoic nodule with well-defined margins and no shadowing.