Chemical induction (4-NQO) of carcinogenesis in the palate of rats: Macroscopic and histopathological analysis

Considering the scarcity of experimental studies related to the induction of carcinomas in the palate, the objective of this study was to analyze the morphological characteristics of carcinogenesis in the hard and soft palate through chemical induction using 4NQO in Wistar rats from the 8th to the 30th week. Five rats were used in the control group and 45 rats in the experimental groups that used 4NQO/propylene glycol diluted in drinking water. The animals were weighed at the end of each week of the experiment. After euthanasia, macroscopic and histopathological analysis of the cases was performed. The greatest evidence of weight gain and subsequent abrupt weight loss was observed between the 22nd and 30th weeks of induction. Macroscopically, we observed a predominance of papillary lesions and a combination of papillary and nodular lesions in both the hard and soft palate. From the 23rd week onwards, there was an increase in the number of lesions across the entire length of the palate. Regarding the diagnosis, there were 28 cases of squamous cell carcinoma (SCC), 14 papillary squamous cell carcinomas (PSCC), 1 case of carcinoma in situ, and 1 case of epithelial dysplasia. It was found that invasion of the connective tissue alone was evident in most cases of palate carcinomas, followed by perivascular invasion. The present study reinforces the efficiency of 4NQO/propylene glycol in inducing carcinogenesis in both the soft and hard palate, with greater evidence of SCC and PSCC in rats, confirming the safety of using the carcinogen and opening up a wide range of possibilities for studies involving palate carcinomas.