We performed a sequential endoscopic examination of esophageal carcinogenesis induced by N-nitrosomethyl-benzylamine (NMBA) in F344 rats. The endoscopic findings were consistent with the histological changes observed in the specimens obtained by a biopsy and/or an autopsy. Seven-week-old male F344 rats received a weekly subcutaneous injection of 0.5 mg/kg NMBA for 15 weeks. The first endoscopic change that was detected was redness of the musosa due to the dilatation of the submucosal blood vessels. Subsequently, the mucosal redness became obscure, and we observed a focal loss of the visible blood vessel network due to hyperkeratosis, followed by the appearance of plaque-like elevated lesions due to acanthosis. Then, smooth and irregular polyps appeared as a result of the development of papilloma without or with dysplastic potential, respectively. Finally, rough elevation appeared as a result of carcinoma in situ and invasive squamous cell carcinoma. The present endoscopic findings correlated closely with the histological changes, indicating that sequential fiberscopic examination may be useful for monitoring esophageal carcinogenesis.

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