Neuroendocrine tumor

Neuroendocrine tumors
Micrograph of a neuroendocrine tumor. H&E stain
Classification and external resources
Specialty	endocrine oncology
ICD-9-CM	209
ICD-O	M8013/3, M8041/3, M8246/3, M8247/3, M8574/3
MeSH	D018358
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Neuroendocrine tumors (NETs) are neoplasms that arise from cells of the endocrine (hormonal) and nervous systems. Many are benign, while some are malignant. They most commonly occur in the intestine, where they are often called carcinoid tumors, but they are also found in the pancreas, lung and the rest of the body.

Although there are many kinds of NETs, they are treated as a group of tissue because the cells of these neoplasms share common features, such as looking similar, having special secretory granules, and often producing biogenic amines and polypeptide hormones.

NETs are believed to arise from various neuroendocrine cells whose normal function is to serve at the neuroendocrine interface. Neuroendocrine cells are present not only in endocrine glands throughout the body that produce hormones, but are found in all body tissues.

Small intestinal neuroendocrine tumors were first distinguished from other tumors in 1907. They were named carcinoid tumors because their slow growth was considered to be "cancer-like" rather than truly cancerous.

However, in 1938 it was recognized that some of these small bowel tumors could be malignant. Despite the differences between these two original categories, and further complexities due to subsequent inclusion of other NETs of pancreas and pulmonary origin, all NETs are sometimes (incorrectly) subsumed into the term "carcinoid".

Enterochromaffin cells, which give rise to carcinoid tumors, were identified in 1897 by Nikolai Kulchitsky and their secretion of serotonin was established in 1953 when the "flushing" effect of serotonin had become clinically recognized. Carcinoid heart disease was identified in 1952, and carcinoid fibrosis in 1961.

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