Forty-three cats with chronic gastrointestinal disease signs had histologic evaluation of full-thickness biopsies from the gastrointestinal tract (GIT) and extraintestinal samples. The GIT samples were one biopsy taken from the fundus of the stomach, duodenum, mid-jejunum, ileum, and descending colon. Extraintestinal samples were collected from the liver, pancreas, mesenteric lymph node, and mesentery. In all the cats, chronic gastrointestinal signs (vomiting, diarrhea, and anorexia) had been present for at least 3 weeks up to 1 year. In 42 of 43 cats, findings revealed different histopathological gastrointestinal alterations on full thickness biopsy, with inflammatory lesions being the most frequent alteration (46.5%). Ten of the 43 cases (23.3%) had diffuse lymphoma diagnosed. In many cases, the demonstration of transmural spread of the neoplastic lymphoid cells is a very helpful method of diagnosing a neoplastic infiltration of the intestinal wall. The mesenteric lymph nodes and liver are frequently involved in cases of diffuse intestinal lymphoma and should be sampled during the laparotomy procedure. Extraintestinal samples are helpful in diagnosing intestinal tumors such as lymphoma and ones of mast cell origin. [VT]