Adenocarcinoma of the posterior segment of the gastrointestinal tract in dogs - clinical, endoscopic, histopathological and immunohistochemical findings.

Of all the tumours in dogs, three percent are located in the intestines, and 36-60% of those tumours affect the large intestine. Adenocarcinomas of the intestines account for 20-35% of the gastrointestinal tumours and for almost 60% of the large intestine tumours. The aim of the study was to analyze clinical disorders and endoscopic, histopathological and immunohistochemical changes in colorectal adenocarcinomas in dogs with the use of the E-cadherin, β-catenin, cytokeratin 20 (CK20), Ki-67 and minichromosome maintenance 3 (MCM-3). The study comprised 11 dogs of both genders and of different breeds diagnosed with adenocarcinoma of the large intestine. They were from 4 to 11 years old. The large intestine adenocarcinoma was diagnosed in all the patients. 72.7% cases were diagnosed with a rectal adenocarcinoma, and 27.3% were found to have a colonic adenocarcinoma. All the studied proteins were expressed at different levels and, together with the histological findings, indicated different levels of malignancy (G). The statistical analysis revealed no statistically significant differences between the expression of E-cadherin and β-catenin in the studied tissues (p=0.79) and between the expression of Ki-67 andMCM-3 (p=0.39). A strong positive correlation was found between the expression of E-cadherin and β-catenin (r=0.86; p<0.05). The diagnosis of adenocarcinomas of the large intestine may be facilitated by the introduction of immunohistochemical studies using appropriate cell markers. They may also aid in the accurate evaluation of the biological character of the tumours, their origin, the connections between tumour cells and the mitotic index. That, in turn, may help determine the malignancy and the choice of treatment.