Immunohistochemistry for the differential diagnosis of renal tumors with oncocytic features

Abstract Objective Histologic analysis of renal tumors usually enables accurate diagnosis, but some tumors may show overlapping histopathologic features, which makes classification difficult. Diagnosis can be extremely challenging in tumors showing oncocytic change, mainly for oncocytomas, chromophobe carcinoma, papillary carcinomas with eosinophilic cells (type 2), and conventional renal cell carcinomas with eosinophilic oncocytic-like cells. The purpose of the present study is to analyze whether the patterns of immunohistochemical expression can help differential diagnosis of these tumors. Material and methods A thorough review of the files of the Department of Surgical Pathology, Fundacion Jimenez Diaz, Madrid, Spain has retrieved 308 records of renal cell carcinomas in the last 12 years, with 15 renal oncocytomas (RO), 28 papillary carcinomas (PRCC), and 13 chromophobe carcinomas (CHRCC). We have performed immunohistochemistry on representative paraffin blocks from 9 oncocytomas, 11 chromophobe carcinomas, 10 papillary carcinomas, and 11 conventional cell carcinomas with oncocytic cells, from which we had suitable material. The immunohistochemical panel included CD117, α-methylacyl-coenzyme A racemase, CD10, p53, progesterone receptors, and cytokeratins 7 and 20. Results Our results show a considerable overlap between immunohistochemical expression in these tumors. Although immunohistochemistry can be helpful in some difficult cases, no markers allow a clear-cut distinction between these tumors, and diagnosis must still rely on morphologic features and histochemical techniques, as well as on molecular techniques when available.