Gastrointestinal (GI) neoplasms are uncommon in dogs and cats, with gastric tumors representing < 1% and intestinal tumors < 10% of overall neoplasms in the dog and cat. Specific etiologic agents for GI neoplasia have not been identified. The increased risk of Belgian Shepherds for gastric carcinoma, and of Siamese cats for intestinal adenocarcinoma and lymphoma, may reflect genetic predispositions. Feline leukemia virus Feline Leukemia Virus Disease $\"Feline$ has been suggested to be an underlying factor in development of feline GI lymphoma, even in cats with a negative retroviral status. Helicobacter infections are associated with gastric neoplasia in people, but similar direct links have not been established in dogs or cats.

Clinical signs of GI neoplasia depend on the location and extent of the tumor and its possible metastases or paraneoplastic syndromes (eg, hypercalcemia, hypoglycemia). The most common clinical signs associated with GI neoplasia include:

Routine laboratory studies and plain radiographs do not show specific changes associated with GI neoplasia. Hypoglycemia is often associated with leiomyomas/leiomyosarcomas. Hypercholesterolemia and increased alkaline phosphatase activity has been seen in some nonlymphomatous neoplasia. Microcytic anemia with or without hypoproteinemia is a common finding with ulcerated masses and chronic blood loss. Electrolyte and acid-base disturbances may reflect ongoing vomiting and can include hypochloremia, hypokalemia, and metabolic alkalosis or acidosis. Paraneoplastic hypercalcemia has been associated with lymphoma and intestinal adenocarcinoma.

Surgical excision of the tumor is the gold standard for nonmetastatic, nonlymphomatous neoplasms, though it can be also performed as palliative care in cases of mechanical ileus secondary to an obstructive mass, even if metastatic disease is confirmed. Curative resection, with margins of ≥4 cm, should be attempted. Careful preoperative discussion is needed before surgery because the perioperative mortality rate is reportedly as high as 50% in cats with intestinal carcinoma. In cats with splenic mast cell tumor with intestinal involvement, splenectomy may also improve the outcome.

Many GI neoplasms are biologically aggressive, with a poor outcome.

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