Background: Renal oncocytoma has several features that overlap with other 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 cytogenetic techniques can be of great use in distinguishing the two tumors, but are difficult to propose as routine methods because of their limited availability.
Objective: To further characterize the histologic criteria of these tumors, we undertook a retrospective study to define the utility of routinely available histochemical and immunohistochemical techniques.
Design and setting: Twenty-one cases of chromophobe cell carcinoma, 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 for lectins; cytokeratin KL1, epithelial membrane antigen, vimentin, S100 protein, and lysozyme) staining.
Results: The antibodies tested and the histochemical staining using Hale's colloidal iron allowed eosinophilic chromophobe cell carcinoma to be distinguished by its characteristic reaction pattern. Seventy-six percent of the chromophobe cell carcinomas showed a microvacuolated pattern, and 89% of the renal oncocytomas 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 apical cytoplasmic positivity was observed in 37% of the renal oncocytoma cases (P = .01). Significant patterns were observed with anti-epithelial membrane antigen and anti-peanut agglutinin antigen antibodies (P = .05 and P = .01, respectively). Positive reactions for vimentin, S100 protein, lysozyme, and UEA-1 were not significant characteristics.
Conclusion: Our study demonstrated that a precise morphologic description associated with simple histochemical and immunohistochemical techniques provides sufficient criteria for a high level of discrimination between the eosinophilic subtype of chromophobe cell carcinoma and renal oncocytoma.