Intestinal Cancer (Adenocarcinoma) in Dogs

Intestinal cancer is fairly rare in dogs. When it does occur, though, intestinal tumors are normally located in the colon and rectum, though sometimes they can be found in the small intestines. Intestinal tumors can be benign or malignant, though adenocarcinomas are malignant. This means they have the potential to metastasize, or spread to other areas of the body. Most animals diagnosed with intestinal tumors are middle-aged or older, and male dogs have a higher predisposition. Certain breeds, such as Collies and German Shepherds, are more likely to develop adenocarcinoma. Possible symptoms of adenocarcinomas include weight loss, diarrhea, and loss of appetite. The most preferred treatment is surgical removal of the tumor, though chemotherapy and anti-inflammatories may be used as alternatives or in conjunction with surgery. Immediately following surgery the dog should be monitored for complication. In many cases of malignant tumors, especially where the tumor has metastasized, dogs only live for anywhere between 3 and 15 months.

Adenocarcinomas are malignant tumors found in the glandular structures in the epithelial tissue. While intestinal cancer is rare in dogs, most intestinal tumors are malignant and therefore, prognosis is not good.

Symptoms of intestinal tumors are usually gastrointestinal signs, and in early stages they may not be distinguishable from other, less serious gastrointestinal diseases. Some of the symptoms of intestinal tumors, including adenocarcinomas, are:

• Weight loss
• Loss of appetite
• Vomiting
• Diarrhea
• Bloody vomit or feces
• Ascites (build-up of fluid in the stomach, causing swelling)
• Feces that appears black or tarry
• Hypoglycemia (low blood sugar)
• Tenesmus (trouble defecating)
• Hematochezia (feces that appear maroon, resulting from blood)
• Peritonitis (inflamed peritoneum)

Types

Most intestinal tumors are malignant, though there are some cases where they are benign, particularly in the rectum, though malignant tumors develop in this location as well. Adenocarcinomas are only one type of intestinal tumors. Others include:

• Lymphoma – cancer of the lymph nodes
• Leiomyosarcoma – a cancer of the connective tissues in the body
• Extramedullary plasmacytoma – a mass of neoplastic monoclonal plasma cells in soft tissue
• Extraskeletal osteosarcoma – rare cancer of the soft tissue
• Mast cell tumors – cancer of a blood cell involved in the body’s response to allergens and inflammation
• Hemangiosarcoma – cancer in the lining of the blood vessels, occurring primarily in dogs and cats

As with most cancers, the cause of adenocarcinoma is not really known. Male dogs ranging between six and nine years in age are more regularly affected than females and other ages. Breed predilection includes Collies and German Shepherds. 

Your veterinarian may do a number of diagnostic tests to rule out other causes and determine the severity of the tumor so the best treatment option can be pursued. Some of these diagnostic tests include: 

• Physical exam
• Abdominal palpation
• Abdominal X-rays
• Abdominal ultrasound
• Blood test
• Chemistry profile
• Laparoscopy (surgery using thin, lighted tube to evaluate abdominal organs)
• Exploratory laparotomy (surgery involving an incision through the stomach wall to see the inside of the stomach)
• Aspirate (drawing of fluid from the stomach using needle)
• Endoscopy (a non-surgical procedure using a tube-like camera to obtain visuals of the digestive tract)
• Exploratory surgery
• Histopathology (a study of a tissue sample obtained from the tumor)

• Surgery is the most likely course of treatment for adenocarcinomas. Full recovery is dependent on complete removal of the tumor, which is often difficult to achieve.
• Chemotherapy may be recommended as an alternative to surgery, especially in cases where tumors have metastasized.
• Prescription of non-steroidal anti-inflammatory medications (NSAIDs) for inflammation reduction. This may also kill tumor cells for carcinomas.
• Special diets or other medications may be used depending on symptoms and accompanying conditions.

Prognosis relies largely on the severity of the tumor and how much it has spread, but in most cases the prognosis is grim. Many dogs with metastatic adenocarcinomas only live around 3-15 months after treatment.