by Ashley Flaman MD and Bibianna Purgina MD FRCPC
March 5, 2023
A paraganglioma is a type of neuroendocrine tumour. It starts from the specialized neuroendocrine cells that are part of the autonomic nervous system.
The symptoms of a paraganglioma depend on the location of the tumour and the type of cells found in the tumour. Some paragangliomas produce hormones which can cause symptoms such as a racing heart, headaches, sweating, and high blood pressure. However, many paragangliomas do not cause any symptoms and are found when imaging such as a CT scan or MRI is performed for an unrelated reason or because the tumour is in a location that can be seen or felt.
Most (about 65-90%) of paragangliomas are non-cancerous tumours. However, some may behave more like cancer by spreading to other parts of the body. Unfortunately, there are no findings that pathologists can see under the microscope that can definitely separate non-cancerous from cancerous tumours with 100% certainty. Therefore, if you are diagnosed with a paraganglioma, you will be asked to follow up regularly with your doctor to ensure the tumour has not spread.
Paragangliomas can be found almost anywhere in the body. However, they are most common in the head and neck (especially around the carotid artery in the neck and in the middle ear), abdomen, pelvis, and chest. A paraganglioma that develops in the adrenal gland is called a pheochromocytoma.
The diagnosis of paraganglioma after some or all of the tumour is removed and tissue from the tumour is examined under a microscope by a pathologist.
When examined under the microscope, a paraganglioma is made up of cells that look similar to one another. The tumour is often surrounded by a thin layer of tissue called a capsule. The tumour cells are usually arranged in round groups that pathologists describe as “zellballen”, which translates from German to mean “cell balls”. The groups of cells are surrounded by specialized cells called sustentacular cells which support the neuroendocrine cells.
Your pathologist may perform a test called immunohistochemistry to confirm the diagnosis. Paraganglioma cells are positive for neuroendocrine markers such as synaptophysin and chromogranin. The sustentacular cells are positive for a protein called S-100.
SDHB (Succinate dehydrogenase complex iron-sulfur subunit B) is a gene that provides instructions for making a protein called succinate dehydrogenase iron-sulfur subunit B. This protein combines with similar proteins (SDHA, SDHC, and SDHD) to form a complex that produces energy for the cell. Some people inherit a genetic syndrome that results in the production of an abnormal SDH protein. These people are also at higher risk of developing paragangliomas.
Pathologists perform a test called immunohistochemistry for SDHB to help identify people who may have inherited this genetic syndrome. A loss of SDHB expression is considered an abnormal result and these people should be referred to a geneticist for further counselling.