Spontaneous lesions of nasal cavity in aging F344 rats and BDF1 mice

The outline of spontaneous lesions of the nasal cavity that were commonly observed in F344 rats and BDF1 mice used as untreated control groups in ten 2-year carcinogenicity studies were presented. In rats, the common spontaneous lesions were eosinophilic change of the respiratory epithelium and the olfactory epithelium, respiratory metaplasia of glands and the olfactory epithelium, foreign body inflammation, deposit of calcium, and thrombus. In mice, the common spontaneous lesions were eosinophilic change of the respiratory epithelium and olfactory epithelium, and respiratory metaplasia of glands and the olfactory epithelium. Some of these lesions revealed either species or sex-related differences of incidence.