SEQUENTIAL MORPHOLOGICAL STUDIES OF THE ESO PHAGEAL CARCINOMA OF RATS INDUCED BY N-METHYL-N-AMYLNITROSAMINE

Abstract

N-Methyl-N-amylnitrosamine was given to 75 male Wistar rats in the drinking water at a concentration of 0.003% for 8 weeks. Three rats were autopsied weekly from the first to the 25th week. The stages of hyperplasia, dysplasia, and squamous cell carcinoma in the esophagus were chronologically observed. Hyperplasia and dysplasia were found by the 6th week and continuously observed until the end of the experiment. Early squamous cell carcinoma was found in the 13th week. They showed endophytic or exophytic growths. Histologically, the endophytic growths were welldifferentiated squamous cell carcinomas and the exophytic growths were poorly-differentiated. Advanced carcinomas were first found in the 15th week and were almost well-differentiated. Carcinomas increased with time, being 9 out of 15 rats (60%) in the final 21st through 25th week. Lymph node metastasis was found in one rat, killed at the 24th week. No differences were found in the location of the esophageal tumors.