Neuroendocrine tumours (NETs) are neoplasms that arise from cells of the endocrine (hormonal) and nervous systems and can arise at many sites in the body.
Types of Neuroendocrine tumours (NETs)
- Gastrointestinal - Gastric, duodenal, pancreatic, small intestine, appendiceal, colon, rectum, ovary, unknown primary.
- Thorax – lung
- Neck/Thorax - Thyroid, parathyroid, thymus
- Pancreas – Non-functioning. Functioning (gastrinoma, Vasoactive Intestinal Peptide [VIP]-oma, insulinoma, somatostatinoma glucagonoma).
- Multiple endocrine neoplasia (MEN) -
- MEN1 - Parathyroid, anterior pituitary, enteropancreatic endocrine cells.
- MEN2A - Medullary thyroid, phaeochromocytoma, primary parathyroid hyperplasia.
- MEN2B - Medullary thyroid, phaeochromocytoma, mucosal neuromas, intestinal ganglioneuromas and marfanoid habitus and other skeletal abnormalities.
- Adrenal - Phaeochromocytoma.
- Extra-adrenal - Paraganglioma.
- Goblet cell – Appendix
- Other - Merkel cell skin cancer, pituitary neuroendocrine tumours.
Neuroendocrine tumours arising within the digestive system are classified as well-differentiated [slower growing] (traditionally referred to as carcinoid tumours when they arose in the tubular gastrointestinal tract and pancreatic neuroendocrine [islet cell] tumours when they arose in the pancreas or, in the case of gastrinomas, in the proximal portion of the duodenum), or poorly differentiated neuroendocrine carcinomas [fast growing] which are generally high grade and can resemble small cell or large cell neuroendocrine carcinoma of the lung.
Pulmonary carcinoids as a whole are well differentiated as opposed to small cell lung carcinoma and large cell neuroendocrine carcinoma, with typical carcinoids sharing some similarities to Grade 1 NETs and atypical carcinoids showing some similarities to Grade 2 NETs of the gastroenteropancreatic tract.
Typical carcinoid has fewer than 2 mitoses/2mm2 and absence of necrosis, and atypical carcinoid has 2-10 mitoses/2mm2 and/or foci of punctate necrosis. Small cell lung carcinoma and large cell neuroendocrine carcinoma have more than 10 mitoses/2 mm2 and extensive necrosis.