Perineural invasion (PNI)

by Jason Wasserman MD PhD FRCPC
April 28, 2022

What does perineural invasion mean?

Perineural invasion (PNI) is a term pathologists use to describe tumour cells attached to a nerve. Nerves are like long wires made up of groups of cells called neurons. Nerves are found all over the body and they are responsible for sending information (such as temperature, pressure, and pain) between your body and your brain.

perineural invasion

Why is perineural invasion important?

Perineural invasion (PNI) is typically only seen in malignant (cancerous) tumours. For this reason, pathologists use PNI as evidence that a tumour is malignant. Perineural invasion is important because the tumour cells can use the nerve to spread into surrounding tissues. This increases the risk that the tumour will re-grow after treatment.

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