Classification of Renal Proliferative Lesions in Rats and/or Mice and Their Diagnostic Problems: Report from the Working Group of the Japanese Society of Toxicologic Pathology

Abstract

The Working Group for the Proliferative Lesions of the Kidney in Rats and Mice was established by the Japanese Society of Toxicologic Pathology (JSTP) to discuss diagnostic problems on renal proliferative lesions in rodents. Members of the Working Group brought many histological specimen and literatures, and compared them with the nomenclatures of renal proliferative lesions in rats recommended by the groups of STP, WHO/IARC/RITA and NACAD proposed in 2000. The Working Group recognized that both of spontaneous and chemical-induced lesions could be categorized by the use of the same diagnostic criteria and classification based on histological and cytological characteristics. The results of histochemical and immunohistochemical examinations indicate that the origins of epithelial proliferative lesions are proximal tubules for basophilic cell type, either proximal or distal renal parts for their clear cell counterpart, and collecting ducts for oncocytic one, whereas the origin of clear cell type is still controversial. The Working Group proposed the modified classification of renal proliferative lesions that were slightly different from the recommendation of international harmonization of rat nomenclature of the kidney proposed by the groups of STP WHO/IARC/RITA and NACAD.