Canine intestinal adenocarcinoma and carcinoid.

Thirty-one of 35 canine intestinal neoplasms were adenocarcinomas and four were carcinoids. Acinar, solid, papillary and mucinous adenocarcinomas were seen. Acinar and papillary adenocarcinomas were more common the duodenum, colon and rectum. Papillary adenocarcinomas involved longer segments of the intestine. Mucinous adenocarcinomas were in all segments of the intestines but were more frequent in the jejunum. The only signet ring cell carcinoma occurred in the duodenum. Carcinoids occurred equally in the duodenum and colon. Half the rectal tumors showed transition from benign polypoid lesions to adenocarcinomas. Hyperplasia, branching of crypts, increase in goblet cells, and glandular fusion (some cells with anaplasia) were severe in the mucosa adjoining all neoplastic tissue. Local invasion was seen in 32 dogs. Lymph node, lungs, liver and intestinal wall were the most common sites of metastases, Half of the metastases in the liver were from carcinoids and were diffuse.