RENAL CHROMOPHOBE CELL-CARCINOMA AND ONCOCYTOMA - COMPARATIVE MORPHOLOGIC, HISTOCHEMICAL, AND IMMUNOHISTOCHEMICAL STUDY OF 124 CASES

Background-Renal oncocytoma has several features that overlap with oth er renal neoplasms, including the eosinophilic subtype of chromophobe cell carcinoma. In fact, strict criteria for renal oncocytoma have not been well defined and remain a matter of controversy. Ultrastructural studies or sophisticated methods such as flow cytometry and cytogenet ic techniques can be of great use in distinguishing the two tumors, bu t are difficult to propose as routine methods because of their limited availability. Objective.-To further characterize the histologic crite ria of these tumors, we undertook a retrospective study to define the utility of routinely available histochemical and immunohistochemical t echniques. Design and Setting.-Twenty-one cases of chromophobe cell ca rcinoma, eosinophilic subtype, and 103 cases of oncocytoma were tested with histochemical (Perls, periodic acid-Schiff, and Hale's colloidal iron) and immunohistochemical (peanut agglutinin antigen and UEA-1 fo r lectins; cytokeratin KL1, epithelial membrane antigen, vimentin, S10 0 protein, and lysozyme) staining. Results.-The antibodies tested and the histochemical staining using Hale's colloidal iron allowed eosinop hilic chromophobe cell carcinoma to be distinguished by its characteri stic reaction pattern. Seventy-six percent of the chromophobe cell car cinomas showed a microvacuolated pattern, and 89% of the renal oncocyt omas showed an apical positivity with Hale's colloidal iron staining ( P < .01). Peripheral cell accentuation reactivity for cytokeratin KL1 was observed in 66% of the chromophobe cell carcinoma cases, and apica l cytoplasmic positivity was observed in 37% of the renal oncocytoma c ases (P =.01). Significant patterns were observed with anti-epithelial membrane antigen and anti-peanut agglutinin antigen antibodies (P =.0 5 and P =.01, respectively). Positive reactions for vimentin, S100 pro tein, lysozyme, and UEA-1 were not significant characteristics. Conclu sion.-Our study demonstrated that a precise morphologic description as sociated with simple histochemical and immunohistochemical techniques provides sufficient criteria for a high level of discrimination betwee n the eosinophilic subtype of chromophobe cell carcinoma and renal onc ocytoma.