Comparative Histopathologic Appearance of UV-Induced Sicin Tumors in Hairless Mice, Crwtothrix Mice, and Fuzzy Rats

Abstract

Squamous cell papillomas and carcinomas occur spontaneously with very low frequency in the skin of laboratory mice and rats. The incidence of tumors is markedly increased with ultraviolet (UV) irradiation. Skin tumors can be produced in animals from varied genetic backgrounds when subjected to simulated sunlight. The incidence within a given stock/strain may be altered by UV dose or by chemical enhancers; less information is available on tumor types as a function of the genetic origin (stock/strain) of animals. The hypotrichotic condition of hairless (hr) mice, cryptothrix (crh) mice, and fuzzy (fz) rats is attained by different mechanisms and the adult skin differs histologically. Others have reported that UV-irradiated skin of shaved haired mice produces a spindle cell tumor of epithelial origin; hr mice develop squamous cell papillomas and carcinomas. Crh mice and fz rats have tumors with histologic features that are influenced by their genetic origin.