Squamous-cell carcinoma and oral, pharyngeal and nasal lesions caused by foreign bodies in feed. Cases from a long-term study in rats

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Abstract
In a carcinogenicity study 443 out of 956 rats had chaff from oat and barley in the mouth between the molars and the gingiva. These foreign bodies caused chronic irritation and inflammation. In 173 animals disruption of tissue caused by the foreign bodies led to pathological communication between the mouth, pharynx and nose. Carcinomas in the oral, pharyngeal or nasal cavity were found in 101 of the 443 animals. Twenty-two animals died and 96 were killed because of intestinal gaseous distension. The intestinal distension was related significantly to the pathological communication between the mouth and pharynx/nose. The study shows that the foreign body-induced chronic irritation and inflammation in the epithelium of the mouth, pharynx and nose can lead to formation of squamous-cell carcinomas. The pathogenesis of the intestinal distension is discussed.