Pathology dictionary -
A neuroendocrine tumour is a type of tumour made up of specialized cells called neuroendocrine cells. Neuroendocrine cells receive information from the nervous system and change the behavior of other cells by making and releasing hormones. Different types of neuroendocrine cells make different types of hormones.
How does a pathologist make this diagnosis?
When examined under the microscope, most neuroendocrine tumours are made up of small to medium sized cells. The genetic material (chromatin) found inside the nucleus of the cell often looks like small dark dots on a white background. Pathologists call this “salt and pepper” chromatin pattern. The cells may stick together to form small structures called glands.
Pathologists sometimes perform a test called immunohistochemistry to confirm that the cells in the tumour are neuroendocrine cells. This test allows a pathologist to see proteins made by the cell. Most neuroendocrine cells make the proteins CD56, synaptophysin, and chromogranin. Tumour cells making these proteins are described as positive (reactive) while those that do not make these proteins are described as negative (non-reactive).
Functional and non-functional tumours
Because they are made up of neuroendocrine cells, some neuroendocrine tumours also make hormones. These neuroendocrine tumours are called functioning. Functioning neuroendocrine tumours can cause symptoms such as diarrhea, nausea, sweating, and head aches. Neuroendocrine tumours that do not produce hormones are called non-functioning. Non-functioning tumours may not cause any symptoms.
Where are neuroendocrine tumours normally found?
Neuroendocrine cells are found throughout the body. A neuroendocrine tumour can start in any location where neuroendocrine cells are normally found. Most neuroendocrine tumours start in the gastrointestinal tract (stomach, small bowel, and colon), rectum (the end of the colon just before the anal canal), appendix, pancreas, and lungs.
Is a neuroendocrine tumour a type of cancer?
The behavior of a neuroendocrine tumour can range from non-cancerous (benign) to cancerous (malignant). Pathologists examine the tumour under a microscope and look for features that will help predict how the tumour will behave.
Microscopic features associated with cancerous tumours include:
Dividing tumour cells – Tumour cells divide in order to create new tumour cells. Mitosis is the word pathologists use to describe a cell that is dividing to create a new cell. A tumour with lots of dividing cells is more likely to behave in an aggressive manner.
Cell death – Cells die when they become very old, injured, or run out of energy. Tumours that are growing very fast have more dying tumour cells than slow growing tumours. Necrosis is a type of cell death that is commonly seen in fast growing and more aggressive tumours.
The risk that the tumour will spread to another part of the body is higher if the pathologist sees dividing tumour cells or cell death. However, all neuroendocrine tumours have the potential to spread or to grow back after the tumour is removed. Tumour cells that travel to another part of the body are called a metastasis.
Types of neuroendocrine tumours
There are different types of neuroendocrine tumours and some are given a special name. The name of the tumour depends on where in the body the tumour starts and the kind of neuroendocrine cells that make up the tumour. Tumours that are more likely to behave in an aggressive manner are called a carcinoma.
Common types of neuroendocrine tumours include:
Lung - Carcinoid tumour.
Lung – Small cell carcinoma.
Adrenal gland - Pheochromocytoma.