A carcinoid is a tumour made up of specialized cells called neuroendocrine cells. Another name for carcinoid is neuroendocrine tumour. Most carcinoids start in the lungs although they can also start in the small bowel (small intestine), colon, or rectum.
Most carcinoid tumours behave like non-cancerous (benign) tumours. However, carcinoid tumours are considered to be a low grade malignancy and all have the potential (even if very low) to spread to other parts of the body.
The cells in a carcinoid tumour all tend to be very similar looking and have a particular chromatin pattern that pathologists describe as “salt and pepper”. The appearance of the cells along with select immunohistochemical stains allow pathologists to make the correct diagnosis.