Experimental tongue carcinoma of rats induced by oral administration of 4-nitroquinoline 1-oxide (4NQO) in drinking water.

Oral administration of 0.001% 4NQO in drinking water resulted in a high incidence of tongue carcinoma in rats. In other major organs, tumor induction was rarely observed. The most frequent site of tongue carcinoma was the dorsum. No metastases were found. Changes observed included carcinoma in situ and invasive carcinoma. Carcinoma in situ showed erosion, leukoplakia, and a gross papillary appearance. Histologically, most carcinomas in situ showed full-thickness alteration of epithelium. Some carcinomas in situ in papillary lesions showed slightly less than full-thickness alteration of epithelium, exhibiting downward, well-differentiated growth. Invasive carcinomas were either endophytic or exophytic. Histologic grading of invasive carcinoma varied from highly to poorly differentiated. The method described offers a new experimental animal model of tongue carcinoma.