What is a schwannoma?

Schwannomas are a common non-cancerous type of tumour that starts in a nerve. It is made up of Schwann cells that normally cover the outside of a nerve. This tumour can occur at any age and in any location in the body.  Sometimes these tumours can be associated with the genetic syndrome neurofibromatosis type 2 (NF2) and people with NF2 are more likely to develop multiple schwannomas. Schwannomas that develop inside the ears are called acoustic neuromas. Other names for this tumour include neurilemoma and neurinoma.

What is a nerve?

Nerves are like long wires made up of groups of cells called neurons. Nerves transmit information (such as temperature, pressure, and pain) between your brain and your body. Nerves are found throughout your body. Some nerves are very small (like those just under the surface of the skin) while others are very large (like those that go to muscles). Nerves are made up of different kinds of cells. Schwann cells are a type of cell that cover the outside of the nerve.

How do pathologists make this diagnosis?

A pathologist may make a diagnosis of schwannoma after a small sample of the tumour is removed in a procedure called a biopsy. The diagnosis can also be made if the tumour is removed completely without a biopsy.

These tumours are usually surrounded by a capsule and are easy to remove by your surgeon. Because they are attached to a nerve, these tumours can cause symptoms such as pain or tingling. Under the microscope, schwannomas are made of spindle cells that look very similar to the Schwann cells that make up a normal nerve.  When pathologists perform a test called immunohistochemistry, the tumours stain strongly for a protein called S100.


Types of schwannomas

There are several types of schwannoma including:

  • Ancient schwannoma – These tumours show microscope features of degeneration.
  • Cellular schwannoma – These tumours have a greater number of Schwann cells inside the tumour
  • Melanotic schwannoma – The tumour cells produce a black pigment which can be seen under the microscope
  • Epithelioid schwannoma – The tumour cells in this type of tumour are rounder or more oval than typical Schwannoma cells.
  • Plexiform schwannoma – The tumour has a more irregular shape because it is made up of a network of interlacing tumour bundles.
by Bibianna Purgina MD FRCPC (updated September 14, 2021)
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