[Non-clear cell renal carcinoma: comparative analysis of the new and old histological classification in 79 cases].

OBJECTIVE: To compare the old classification and 2004 WHO histological classification of renal cell carcinoma, summarize the differences and possible reasons, and correct the traditional pathological concepts of kidney cancer. METHODS: Specimens of 79 cases histopathologically diagnosed as non-clear cell renal cell carcinomas after radical nephrectomy during 1998 to 2005 in Tianjin Medical University Cancer Hospital were reclassified according to the 2004 WHO renal cell carcinoma histological classification system. RESULTS: After reclassification, there were 14 cases of clear cell renal cell carcinoma (CCRCC), 23 cases of papillary renal cell carcinoma (PRCC), 34 cases of chromophobe renal cell carcinoma (ChRCC), one collecting duct renal cell carcinoma, one unclassified renal cell carcinoma, 5 cases of mixed cell renal cell carcinoma (CCRCC + PRCC 2 cases, CCRCC + ChRCC 2 cases, PRCC + ChRCC 1 case), and one oncocytoma diagnosed. CONCLUSIONS: Some chromophobe renal cell carcinomas and papillary renal cell carcinomas were easier to be diagnosed as granular cell renal cell carcinoma in the past. The eosinophilic cytoplasm similar to that in the granular cells, and some confusion between PRCC and ChRCC are the main reasons. The cellular characteristic features of granular renal cell carcinoma can be found in many types of renal tumors. Granular cell renal cell carcinoma is not an independent entity, therefore, it should be removed from the histological classification of renal cell carcinoma. The diagnosis standard of mixed renal cell carcinoma (MRCC) need to be determined and consummated.