Renal Tumors in Mice: Light Microscopic Observations of Epithelial Tumors Induced by Ethylnitrosourea

Renal epithelial tumors developing in (C3HeB/FeJ × A/J)F1 and (C57BL/6J × C3HeB/FeJ)F1 mice after a single postnatal injection of l-ethyl-l-nitrosourea (ENU) are described. Most of these neoplasms were benign and resembled the corresponding human renal adenomas in morphology and biologic behavior. Three morphologic variants were distinguished by papillary cystic, platelike, or tubular patterns of growth. Most adenomas had a papillary cystadenomatous architecture and about a third were bilateral. Malignancy was not evident from this common morphologic variant, though some papillary cystadenomas reached dimensions greater than those of the normal kidney. In contrast, pulmonary metastases were observed from both tubular and platelike granular or “clear-cell” neoplasms. Hyperplasia ot the proximal convoluted tubular epithelium with or without cystic dilatation of the tubule and infoldings of the epithelium was recognized as a preneoplastic lesion. Morphologic and staining characteristics of cells from early microscopic lesions indicated that both papillary cystic and solid-cell tumors originated from proximal convoluted tubular epithelium.