Clinical signs of intestinal tumors generally develop slowly starting with loss of weight and appetite. Usually diarrhoea and vomiting follow with secondary symptoms including fluid swelling of the abdomen and anaemia.

Adenocarcinomas are seen predominantly in older animals with an increased incidence in males. These tumors lead to thickening of the gut which may grow both outwards to form a mass or inwards to block the intestine. Ulceration of the gut lining is also common producing black faeces and occasionally anaemia. These tumours readily spread to local lymph nodes (glands) draining the intestine and are capable of spreading (metastasizing) to other parts of the body.

Identifying the tumors can be difficult without surgically removing part of the intestine for examination (biopsy). Xrays may identify a mass or thickening but these can resemble other obstructions.

Because of the tendency for adenocarcinomas to spread the outlook for animals with this tumor is generally poor. Average survival time after surgery is quoted at 4-6 months.

Lymphosarcomas can occur at any age but are also more common in older animals and males. Both a diffuse form which causes extensive thickening of the gut and a nodular form which produces localized narrowing and obstruction of the gut are recognized. As with adenocarcinomas ulceration of the lining may be seen and spread to lymph nodes is common. Unfortunately lymphosarcomas are also cancerous spreading to a large number other organs relatively early in their course making the outlook for this disease poor.

Clinical signs, Xrays, and laboratory tests showing increased white blood cells (neutrophils), liver enzymes, and low blood protein, may suggest lymphosarcoma however diagnosis is eventually made by biopsy of the effected intestine.

Lymphosarcomas are one tumor which is very sensitive to chemotherapy in dogs and cats. Recent studies have indicated this treatment may offer a more reasonable long term prognosis for animals with intestinal lymphosarcoma in combination with surgical removal of the effect gut.