Infiltrative rectal adenocarcinoma in a dog

ABSTRACT

Background: Intestinal neoplasms are uncommon in dogs and adenocarcinoma is the main histological type found. Thisneoplasm presents slow growth and high capacity of causing metastasis. Histologically speaking, neoplasm cells can presentsolid, tubular, papillary arrangement and note amorphous extra-cellular material. Clinically observed tenesmus, diarrhea,dyskinesia, hematochezia, mane, protrusion of the anus, weight loss, anorexia. The occurrence and clinicopathologicalaspects of tumors in dogs’ gastrointestinal tract, the rectal segment, remains poorly understood. Accordingly, the aim ofthe present study is to report a case on infiltrative rectal adenocarcinoma diagnosed in a dog.Case A 7-year-old male dog representative of the Fila Brasileiro breed was presented to the Veterinary Hospital of University Federal Rural of Amazonia, with history of hyperthermia, anorexia, apathy and tenesmus. Imaging examinationsdepicted prostatomegaly. Exploratory laparotomy was performed and showed the thickening and hardening of the rectumsegment. The animal was subjected to euthanasia. Necroscopy showed increased rectal perimeter; the mucosa in its opening presented atypical cerebroid aspect and irregular surface, and areas dark red. The rectal segment depicted a thick wallof white color, irregular limits covering the muscular and adjacent sub-mucosa. The peri-rectal adipose tissue presentedpoor delimitation with the rectum, multiple greyish and reddish areas. Increased prostate and iliac lymph, and multi nodeof regular limits in the lungs. The histology of the rectal tissue depicted epithelium with differentiated neoformation,composed of atypical cells; nuclear anisocytosis, anisocariasis and hyperchromasia placed in small islands, cords or tubular formation. Neoplasm growth was unorganized and of infiltrative character. Some areas presented mucosal patterncells with Signal Ring morphologic. Multiple rectal blood...