Apudomas in Dogs

Apudoma is a type of Neuroendocrine Tumor or NET. Neuroendocrine cells exist all over the body. They secrete various hormones which regulate the metabolism of food as well as other bodily processes. They are capable of storing hormones and releasing them into the body as needed. Apudomas are cancerous tumors that form on some neuroendocrine cells, specifically APUD (Amine Precursor Uptake and Decarboxylation) cells in the gastrointestinal tract and pancreas. This type of cancer is rare in dogs, but there are a few recorded cases. In general, the cancer develops relatively slowly, but, by the time it is discovered, metastasis has often already started. Typically the condition will eventually end up being fatal, but it may be able to be managed for months or even years after diagnosis.

Apudoma is defined as a cancerous tumor that forms on certain neuroendocrine cells in the gastrointestinal tract and pancreas. There are many types of GI cancer which produce similar symptoms in dogs, but apudomas can sometimes be identified by increased acid reflux and ulcers.

Apudomas exhibit many symptoms common to almost all forms of GI cancer. Some neuroendocrine tumors, however, can secrete excessive amounts of certain hormones that affect digestion and metabolism. Hypersecretion of gastrin is most common leading to problems with gastric reflux and peptic ulcers. If you notice any of the following symptoms in your dog, discuss them with a veterinarian as soon as possible:

• Weight loss
• Excessive vomiting
• Vomiting with blood
• Diarrhea
• Depression
• Lethargy
• Pain in the abdomen
• Dried blood in the stool (melena)
• Fresh blood in the stool (hematochezia)
• Acid reflux
• Ulcers
• Gastritis

Types

Concepts of neuroendocrine cells have been re-evaluated over the years, but there remain some differences in nomenclature. At one time all neuroendocrine cells were believed to be APUD cells, and all NET were referred to as apudomas. This theory has since been disproved, and apudoma would most aptly refer to a gastrinoma or some type of carcinoid. The two other types of pancreatic cancer listed below could be relevant if you notice different symptoms: 

• Gastrinoma (Gastric Islet Cell Tumor) – a NET that forms on the APUD cells in the pancreas and leads to overproduction of gastrin and subsequent ulceration of GI tract mucosa.
• Carcinoid – a group of NET’s which occur throughout the GI tract, but have been found most commonly in the stomach among dogs. In humans, carcinoids have led to excessive production of histamine, but increased hormone production hasn’t yet been noted in dogs.
• Insulinoma (Functional Islet Cell Tumor) – a NET found on the insulin producing cells in the pancreas. It often leads to excessive insulin production and symptoms of hypoglycemia.
• Glucagonoma – a NET found on the glucagon producing cells in the pancreas which can result in skin lesions on the bottoms of the feet, leg joints and abdomen.

There isn’t a known cause for apudoma or any other type of cancer in dogs. It’s more common among older dogs. Hereditary, diet, and lifestyle factors may play a part, but this is difficult to evaluate especially with a rare form of cancer.

Your veterinarian will run complete blood and urine tests which will often show anemia, uremia or increased blood toxicity levels. X-rays or ultrasound will be used to check for tumors and evaluate the level of metastasis. CT scans or an MRI could also be ordered if X-ray results are inconclusive. The vet may need to perform exploratory surgery to find tumors on the pancreas, especially if high levels of gastric acid are among your dog’s symptoms. 

Biopsies will likely be necessary to evaluate the cells at a microscopic level. The veterinarian may order an endoscopy for this purpose. This is an invasive test that involves inserting surgical equipment and a camera down the throat. This will be a separate appointment and your dog will need to fast and have an anesthetic.

Any information you can give the veterinarian on the nature and onset of your dog’s symptoms will be extremely helpful in indicating the possibility of cancer. It will likely take several appointments, however, and a number of tests, to identify the specific type of cancer and make an accurate diagnosis.

Removal of the tumor is the best treatment option, but this will depend on the recommendation of the veterinarian. Many tumors have spread beyond an operable point by the time they are diagnosed. Symptoms of excessive gastrin secretion can often be effectively managed with an antacid, such as famotidine or omeprazole. Since this type of cancer develops slowly, your dog may lead a fulfilling life for some time until further symptoms manifest.

If the veterinarian recommends surgery, your dog will spend several days in hospital after the surgery for monitoring. Oxygen, fluids, antibiotics and other medication will be given as needed. After returning home, the recovery period will last 2 to 3 weeks. Your dog will be prescribed pain medication, and probably an antacid. You will need to check the incision daily and monitor for signs of tearing. He will likely need a check-up with the veterinarian in several weeks.

In some cases the veterinarian may recommend chemotherapy after surgery to reduce metastasis. This usually involves three or four sessions at 2 to3 week intervals. The medication is typically given by injection, but the appointment will last 1 ½ to 2 hours to allow for monitoring and further tests. Dogs do not normally exhibit hair loss, but they may have quite severe gastrointestinal side effects.

If the tumor was not operable, the vet will continue to check on its progression and adjust medication as necessary. It may take some time before your dog has significant pain or symptoms that cannot be treated. 

Even if surgery is successful in removing your dog’s tumor, continued medical check-ups will still be necessary. Cancer often returns, and there may have been metastasis that wasn’t noted at the time of operation. Diagnosing any further developments early is essential for continued treatment. 

It’s rare to make a full recovery from cancer, but the tumors may remain in remission for quite some time. Since this isn’t a common type of cancer, there aren’t extensive studies on its progression. The veterinarian will need to evaluate your dog’s specific case in order to make an accurate prognosis.