Synaptophysin is a protein found on the surface of certain cells in the body. It is especially important in cells that help send signals in the nervous system, such as nerve cells (neurons) and some related types of cells. Synaptophysin is a marker that pathologists use to identify specific types of cells and tumours under a microscope.
What types of normal cells and tissues express synaptophysin?
Synaptophysin is normally expressed in cells that play a role in transmitting signals within the nervous system. These include:
- Neurons: These are the central cells of the brain and spinal cord responsible for processing and transmitting information.
- Neuroendocrine cells: These are specialized cells that release hormones in response to nerve signals. They are found in various tissues, such as the adrenal glands, pancreas, and gastrointestinal tract.
What types of noncancerous tumours express synaptophysin?
Some benign (non-cancerous) tumours express synaptophysin because they arise from cells that naturally produce this protein. Examples include:
- Ganglioneuroma: A tumour made up of mature nerve cells and supportive tissue.
- Paraganglioma: A tumour that arises from neuroendocrine cells, often found near blood vessels.
- Pituitary adenoma: A tumour in the pituitary gland, which sometimes expresses synaptophysin due to the neuroendocrine origin of the gland.
- Adrenocortical adenoma: A tumour of the adrenal cortex that is typically non-cancerous but may produce hormones.
- Parathyroid adenoma: A benign tumour of the parathyroid glands, which can sometimes express synaptophysin due to its endocrine nature.
What types of cancerous tumours express synaptophysin?
Synaptophysin is commonly expressed in certain malignant (cancerous) tumours, particularly those arising from nerve, neuroendocrine, or endocrine cells. These include:
- Neuroendocrine tumours (NETs): These tumours can occur in various organs, such as the lungs, pancreas, and gastrointestinal tract.
- Small cell carcinoma: A highly aggressive cancer often found in the lung but can occur in other organs.
- Neuroendocrine carcinoma: A high grade cancer that arises from neuroendocrine cells, often found in the lung or gastrointestinal tract. These tumours tend to behave aggressively and require specialized treatment.
- Merkel cell carcinoma: A rare but aggressive skin cancer that arises from neuroendocrine cells in the skin.
- Medullary thyroid carcinoma: A type of thyroid cancer that arises from the neuroendocrine C cells, which produce calcitonin.
- Adrenocortical carcinoma: A rare cancer that originates in the adrenal cortex and may occasionally express synaptophysin.
- Neuroblastoma: A cancer that usually occurs in children and arises from immature nerve cells.
- Medulloblastoma: A type of brain tumour that is common in children.
- Pheochromocytoma: A tumour of the adrenal gland that arises from neuroendocrine cells.
How do pathologists test for synaptophysin, and how will the results be described?
Pathologists test for synaptophysin using immunohistochemistry (IHC). This process involves treating a tissue sample with special antibodies that bind to synaptophysin if it is present. The binding is visualized under a microscope, often appearing as a brown or red stain on the cells that produce the protein.

In your pathology report, the results may be described in terms of whether the tumour cells are positive or negative for synaptophysin. The intensity (weak, moderate, or strong) and pattern (diffuse or focal) of staining may also be mentioned. For example:
- Positive for synaptophysin: Indicates the tumour cells produce synaptophysin, supporting a diagnosis of a neuroendocrine or neuronal tumour.
- Negative for synaptophysin: Suggests the tumour cells do not produce this protein, ruling out certain tumours.
Understanding whether a tumour expresses synaptophysin helps pathologists and doctors make an accurate diagnosis and guide treatment decisions.
About this article
Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.