Neuroendocrine Tumors: Gastrinomas and Intestinal Carcinoids
What are neuroendocrine tumors?
Neuroendocrine tumors develop due to disorganized, uncontrolled proliferation of neuroendocrine cells, which are special cells that make up the neuroendocrine system.
Neuroendocrine cells are like nerve cells (neurons), but they also make hormones like cells of the endocrine system (endocrine cells). They receive messages from the nervous system and respond by making and releasing hormones. These hormones enter the blood and travel all over the body to control many body functions.
Neuroendocrine tumors can be benign (non-cancerous and only grow locally) or malignant (cancerous and spread to other areas of the body).
- Functional tumors over-secrete their normal hormone products and cause signs of disease due to excessive hormone levels.
- Non-functional tumors cause signs of disease due to the presence of a physical mass and/or metastasis (spread to other areas of the body).
A growing tumor can damage the nearby healthy tissues, even if it’s benign, and can sometimes secrete excess hormone. Generally, neuroendocrine tumors are rare in dogs and cats. Very rarely, more than one type of neuroendocrine tumor may occur at the same time.
What is a gastrinoma and what clinical signs does it cause?
A gastrinoma is a neuroendocrine tumor that occurs in the pancreas or duodenum (upper intestine) in the cells that produce gastrin — a hormone that stimulates stomach acid production.
A gastrinoma releases excessive stomach acid that causes ulcers (openings in the lining of the stomach). If your pet has gastric ulcers, you may see a loss of appetite, vomiting (sometimes with blood), diarrhea, weight loss, and signs of dehydration.
What is an intestinal carcinoid and what clinical signs does it cause?
An intestinal carcinoid is a tumor that occurs in cells located throughout the intestinal tract that release serotonin — a hormone needed to regulate intestinal movement (peristalsis) and fluid secretion that aids digestion.
Like gastrinomas, intestinal carcinoids can cause appetite loss, vomiting, diarrhea, and weight loss. As the carcinoids get larger, they can cause an intestinal obstruction (blockage).
How are these tumors diagnosed?
These tumors may be diagnosed in a variety of ways.
- Bloodwork may point to a gastrinoma if there is ulcer-related blood loss and if there are higher than normal levels of gastrin in the blood.
- Imaging may be needed to identify the presence of a tumor, including radiographs (X-rays), ultrasounds, computed tomography (CT scans), and magnetic resonance imaging (MRI). Imaging may demonstrate one or more masses or signs that a tumor has spread to other areas of the body, such as the lungs. Some neuroendocrine tumors are found while taking images for a completely different reason.
- Tissue biopsy is needed to definitively diagnose these tumors. A tissue biopsy involves taking a small sample of tissue from the body for examination under a microscope. The tissue may be obtained by surgically removing the entire tumor or a portion of the tumor. To identify the type of cancer, a veterinary pathologist examines the tumor or pieces of the tumor under the microscope, a process called histopathology.
For neuroendocrine tumors, special procedures are often necessary to make a diagnosis. Histopathology is not only helpful in making a diagnosis, but can indicate how the tumor is likely to behave.
How do these tumors typically progress?
Both tumors have the tendency to metastasize (spread to other areas of the body). Common sites of metastasis include the lymph nodes, liver, heart, pancreas, and spleen.
Staging (searching for potential spread to other locations in the body) is highly recommended for these tumors. Staging may include bloodwork, urinalysis, X-rays of the lungs, abdominal ultrasound, or other imaging procedures. If any lymph nodes are enlarged or feel abnormal, further sampling may be pursued to determine if spread is present.
What are the treatments for these tumors?
Treatment depends on the type, size, and malignancy of the tumor, as well as the presence of metastasis. Treatment typically involves several options, including surgery, chemotherapy, radiation therapy, and medical and dietary approaches. Your veterinarian may refer your pet to a veterinary oncologist to develop a care plan.
Gastrinomas may be treated medically if surgery is not an option, using medications to suppress gastric acid production and protect the lining of the stomach.
Is there anything else I should know?
Neuroendocrine tumors are rare, so if they are suspected or diagnosed, your veterinarian may refer you to a veterinary oncologist. Many of the signs of these tumors are symptomatic of many common illnesses, and the signs may come and go, so these tumors can be difficult to diagnose.
As metastasis has generally occurred by the time of diagnosis, prognosis with gastrinomas or intestinal carcinoids is guarded, and a positive response to treatment is less certain.
© Copyright 2025 LifeLearn Inc. Used and/or modified with permission under license. This content written by LifeLearn Animal Health (LifeLearn Inc.) is licensed to this practice for the personal use of our clients. Any copying, printing or further distribution is prohibited without the express written consent of LifeLearn. This content does not contain all available information for any referenced medications and has not been reviewed by the FDA Center for Veterinary Medicine, or Health Canada Veterinary Drugs Directorate. This content may help answer commonly asked questions, but is not a substitute for medical advice, or a proper consultation and/or clinical examination of your pet by a veterinarian. Please contact your veterinarian if you have any questions or concerns about your pet’s health. Created on Jul 24, 2025.