LAUSR

A 62-year-old man underwent a right radical nephrectomy for an incidentally discovered right renal tumour. Macroscopic examination of the specimen demonstrated an 11 cm diameter, well-circumscribed, tan-brown, solid tumour with focal haemorrhage. On immunostaining, the tumour cells were positive for AE1/AE3, Epithelial Membrane Antigen (patchy) and PAX8. No immunoreactivity was seen with CK7, CK20, CA9, CD10, CD117, AMACR, Melan A and HMB45. Review the high quality, interactive digital Aperio slide at http://virtualacp.com/JCPCases/jclinpath-2019-206260/ and consider your diagnosis. 1. Eosinophilic solid and cystic renal cell carcinoma (RCC). 2. Eosinophilic variant of chromophobe carcinoma. 3. Eosinophilic variant of conventional (clear cell) RCC. 4. Oncocytoma. 5. Succinate dehydrogenase (SDH)-deficient RCC. The submitted section shows a well-circumscribed unencapsulated tumour with a pushing border and peripheral entrapment of renal tubules (figure 1A,B). The tumour is composed of tightly packed cells with abundant, predominantly eosinophilic cytoplasm arranged in sheets and nests with cystic areas (figure 1C). No papillary architecture is seen. Many of the cells show a degree of cytoplasmic clearing, and cell boundaries are generally indistinct. The nuclei are generally uniform and round with occasional small nucleoli (figure 1D). Figure 1 A well-circumscribed pseudoencapsulated lesion (A) with a pushing border and peripheral entrapment of renal tubules (B). The tumour shows a closely packed, solid-microcystic architecture (C) composed …