Carcinoid Cancer in Cats

By PetMD Editorial on Jan. 12, 2009

Carcinoid Syndrome and Tumor in Cats

Carcinoid tumors are rare, slow growing tumors that are formed by the endocrine cells in the mucosal lining of organs, such as the stomach and intestine. These tumors are small neuroendocrine tumors, typically of the gastrointestinal tract, that secrete serotonin, a naturally occurring neurochemical that is usually associated with sleep and memory functions.

Carcinoid tumors secrete the amines serotonin and histamine into the bloodstream, as well as a number of peptides - chemical compounds such as bradykinins and tachykinins, which are responsible for tissue contraction. Carcinoid tumors are rare in animals, but when they do occur it is generally after a cat has reached seven years of age.

Symptoms and Types

Primary carcinoid tumors are usually found in the stomach, small intestine, liver, and heart. The general clinical symptoms of carcinoid tumors include anorexia, vomiting, dyschezia, weight loss due to liver failure, and heart disease.


As with many types of cancers, the actual causes and risk factors for carcinoid tumors are unknown. Clinical signs in cats can vary greatly, depending on the location of the tumor and how far the metastasis has advanced. The size of the tumor and how it may be impeding the functionality of the organ it resides in will also have a lot of influence on how ill your pet feels, and whether or not it will be fatal.


There are a variety of ways to diagnose carcinoid tumors. An intestinal tumor may cause some of the same symptoms as primary gastrointestinal diseases, such as neoplasias, dietary indiscretions, parasites, and inflammation related to any other condition. Therefore, a differential diagnosis will be necessary — meaning that your doctor will base the findings on a process of elimination, using both the symptoms and the results of tests. Biochemical tests and urine analysis may yield normal results, with the exception of a mild non-regenerative anemia, electrolyte abnormalities, and elevated liver enzymes. An ultrasound image may lead to the identification of primary tumors and metastasis in the abdomen and thorax. However, a definitive diagnosis can only be made with a biopsy of the affected tissues. An electron microscopy, and immunohistochemical stains can help to confirm the diagnosis by identifying the substances that are typically secreted by carcinoid tumors.



Sometimes, complete surgical removal of the tumor can cure the condition. Reducing the size of the tumor through surgery may also help to eliminate any gastrointestinal symptoms that are being caused by the obstruction of a large tumor. There are no other standard therapies for treating carcinoid tumors, but your veterinarian may have some treatment options available that will help to keep metastasis to a minimum, or to help make your pet comfortable.

Living and Management

If a tumor can not be completely removed, routine blood tests will need to be conducted to determine whether destructive hepatic metastasis is occurring. A yearly ultrasound is also recommended for monitoring progress, so that if any metastasis has occurred in the liver, or in other organs, it can be treated promptly, before organ functionality is reduced. 

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