Neuroendocrine cells are characterized by their ability to produce and secrete a neuromodulator, transmitter, or hormone. In addition, these cells contain dense core secretory granules, the storage site for the secreted product(s). Neuroendocrine cells can release this product in a regulated manner by classic exocytosis. Neuroendocrine cells differ from classic neurons because they lack axons and synapses. Certain molecules, particularly those of the granin family (eg, chromogranin), are synthesized and stored in neuroendocrine cells and serve as immunohistologic markers.
Previously, neuroendocrine cells were classified as amine precursor uptake and decarboxylation (APUD) cells and were believed to be solely derived from neuroectoderm. However, more recent evidence supports a more diverse embryologic origin.
Tumors that arise from this cell type comprise a family of neuroendocrine tumors. Because of the diffuse distribution of cells, particularly within the GI tract, NETs are found in a wide variety of locations. Overall, NETs are rare tumors in people and animals. Some NETs oversecrete their normal product, and the excessive levels result in the observed signs. Other NETs are nonfunctional, and clinical signs instead result from physical forces associated with expansion and/or metastasis.
Insulinoma and Gastrinoma
Insulinoma (functional islet cell tumor) is the most common neuroendocrine tumor in domestic species. See discussions of insulinoma Functional Islet Cell Tumors in Small Animals Islet cell tumors are the most common cause of hypoglycemia in older dogs. Clinical signs vary but often consist of weakness, ataxia, collapse and seizures. Diagnosis is by documenting hypoglycemia... read more 
and gastrinoma Gastrin-secreting Islet Cell Tumors in Dogs and Cats Gastrinomas are functional tumors of the pa s that secrete the hormone gastrin. They are rare but have been reported in people, dogs, and a cat. Hypersecretion of gastrin in people results in... read more .
Carcinoids
Carcinoids are a heterologous group of NETs that occur in various regions of the GI tract, liver. lung, and occasionally heart. In dogs and cats, carcinoids have been reported to occur in the stomach. The most common signs reported in affected animals include chronic vomiting, anorexia, diarrhea, and weight loss. In people (but not yet documented in companion animals), carcinoids serve as a source of serotonin or histamine. Excessive release of these transmitters can cause a syndrome of flushing, hypotension, wheezing, and diarrhea in people. In dogs and cats, carcinoids may cause obstruction in the GI tract and/or metastasize to lymph nodes and other tissues.
Glucagonoma
Glucagonomas have been found in a small number of dogs. Metastasis to liver and lymph nodes is common. Interestingly, affected animals show cutaneous lesions characterized by a superficial necrolytic dermatitis affecting mucocutaneous junctions, footpads, elbows, or the abdomen.
Key Points
Insulinoma is the most common neuroendocrine tissue tumor in domestic species.
Carcinoids found in the GI tract can cause nonspecific GI signs, including vomiting, anorexia, and weight loss.
Glucagon-secreting tumors are often associated with a superficial necrolytic dermatitis affecting mucocutaneous junctions.
For More Information
See our pet health information regarding neuroendocrine tissue tumors in dogs Neuroendocrine Tissue Tumors in Dogs Neuroendocrine tissues are tissues that have both nervous system and hormone-producing functions. They are found in a number of locations throughout the body. Tumors develop occasionally from... read more and in cats Neuroendocrine Tissue Tumors in Cats Neuroendocrine tissues are tissues that have both nervous system and hormone-producing functions. They are found in several locations throughout the body. Tumors develop occasionally from neuroendocrine... read more .
