Histopathology and Mainz Classification of Renal Cell Tumors: A Histogenetic Study and DNA Content Analysis

ABSTRACT

The Mainz classification for renal cell tumors was introduced in 1986 and it's utility has been reported in several histogenetic and genetic studies of renal cell tumors. We present a study of 127 cases of renal cell tumors with clinicopathologic correlation, DNA content analysis, and histogenesis studied by histochemical and immunohistochemical staining. The 127 renal cell tumors classified by the Mainz classification were 87 clear cell, 17 chromophilic, 13 chromophobe and 3 sarcomatoid renal cell carcinomas, 5 oncocytomas and 2 adenomas. These subtypes showed significant correlation not with age, sex, Robson's stage, DNA ploidy or tumor recurrence but with nuclear grade (p=0.001) and tumor size (p=0.001). Hall's colloidal iron (p=0.002) and carbonic anhydrase II (p=0.013) stains, representing the origin of distal nephron especially of collecting duct, were significantly correlated with specific subtypes of renal cell tumors, especially chromophobe cell renal carcinoma. This study demonstrates that the Mainz classification suggests several morphologically different subtypes and variants of renal cell tumors and that some of them may have originated from the distal nephron, particularly from the collecting duct.