Validation of a new experimental model of colon cancer

Background: Most of the published animal studies that have evaluated tumor growth and port site metastases in laparoscopy have utilized a cell suspens ion model and thus cannot be compared to the clinical situation. Although s olid tumor models have been developed, there has been no experimental model that establishes an orthotopic tumor in the rectum, reflecting the clinica l situation of a solid colonic cancer. Methods: Tumor cells (colon adenocarcinoma DHD/Kl/ TRb) were administered i ntraperitoneally in rats, which were used as solid tumor donors. A 20-mg pi ece of solid tumor from the donor was placed in a submucosal blister create d in the rectum wall of the study rats. The approach to the submucosal blis ter was made through the mucosa after contralateral enterotomy. In order to validate the model, this intervention was performed in 10 cases (group A). After 10 days of intervention, the rats were submitted to resection of the rectum and histological examination of the specimen. In another 10 rats (g roup B), manipulation of the tumor was performed after 10 days to cause tum or cell spillage. The likelihood of tumor dissemination was investigated in this group 20 days after this intervention. Results: Group A developed solid tumors in seven of 10 cases (70%). All of the tumors were localized between the muscular and the mucosal layer, with preservation of the serosa and without affecting the enterotomy. In all of the rats in group B, macroscopic tumor was observed in the upper rectum (10 0%) 10 days after its induction. Twenty days after tumor manipulation, nine rats had local tumor dissemination; two of them also had general tumor dis semination in the abdominal cavity. Conclusions: We established a novel solid colonic tumor model in rats for t he investigation of intraoperative tumor cell spillage during resection of the colon and the development of port site metastases.