Primitive neuroectodermal tumour (PNET) | Cancer Research UK
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Primitive neuroectodermal tumour (PNET)

Primitive neuroectodermal tumours (PNET) are cancerous tumours that most commonly develop in the brain or spinal cord in children or young adults. There is information on this page about


What PNET is

PNET (pronounced pee-net) stands for a group of tumours known as Primitive Neuro Ectodermal Tumours. Doctors use this term to group these tumours together because the tumour cells look similar under a microscope.

PNETs develop from cells that are left over in the body from the earliest stages of the development of the nervous system. Normally these cells are harmless. But occasionally they turn into a cancer. These cancers are more common in children than adults.

Doctors use the term PNET to classify the tumour. They are divided into two main groups

  • PNETs of the brain and central nervous system
  • Peripheral PNETs (outside the brain and nervous system)

PNETs of the brain or spinal cord

Primitive neuroectodermal tumours that occur in the brain and spinal cord include

  • Medulloblastoma, which develops in the back part of the brain – the cerebellum
  • Pineoblastoma which develops deep in the middle of the brain, in the area of the pineal gland (which is close to the pituitary gland)
  • Central nervous system PNET, which develops in the upper part of the brain (the forebrain or cerebrum)

Diagram showing the parts of the brain

Medulloblastoma is the most common PNET to occur in the brain or spinal cord. You can find detailed information about treating primitive neuroectodermal tumours in the treating brain tumours section.


Peripheral PNETs

Doctors used to use the term peripheral PNET to describe these tumours when they occur in the soft tissues of the body. But the tumours have the same genetic change as Ewing's sarcoma of the bone and so they are now called soft tissue Ewing's sarcoma.


Research into PNETs

Doctors are researching new ways of treating primitive neuroectodermal tumours. Some trials are taking place at the moment. To find out more about the trials, go to our clinical trials database and type ‘PNET’ into the advanced search box.


Side effects of treatment

All treatments have side effects. These usually happen during treatment or very soon afterwards. There are medicines to help control most of these immediate side effects so tell your doctor or nurse if you have any. You can find information about the possible side effects of chemotherapy and side effects of radiotherapy treatment in the cancer treatment section.

Many parents worry about possible long term effects of treatment on their child. Some children treated for PNET go on to develop long term side effects. But not everyone has them. The possible long term effects depend on

  • The position of the PNET in the body
  • The type of treatment the child has had
  • The treatment doses they had
  • The age they were when they had treatment

It is important to remember that the risk of these long term effects is small. And the risk needs to be weighed up against the benefits of treatment. For many children, treatment will cure their cancer.

The risk of long term effects is also becoming less as treatments improve. So the treatment that children have now is less likely to cause long term problems than treatment in the past.


Possible long term side effects

Possible long term effects of treatment include

  • Difficulty fathering a child or becoming pregnant
  • Changes in how the lungs and heart work
  • Problems with bone growth in areas treated with radiotherapy
  • A small risk of developing a second cancer some years later

Your doctor will talk to you about the possible risks depending on the treatment you had. If the patient was your child, the treatment team will continue to keep a close eye on them so that if any problems occur they can be treated early.

The Scottish Intercollegiate Guidelines Network (SIGN) and the National Institute for Health and Care Excellence (NICE) have produced guidelines about how children should be monitored after childhood cancer. These include recommendations about which professionals should be involved in monitoring the child into their adult life. The Children’s Cancer and Leukaemia Group (CCLG) has also produced information about long term follow up to guide doctors on how best to do this.


Research into long term side effects

Researchers are looking into the long term effects of treatment for all types of childhood cancer. The Centre for Childhood Survivor Studies is carrying out the British Childhood Cancer Survivor study. This research is looking at children who were diagnosed with cancer between 1940 and 1991 and lived for at least 5 years after diagnosis.

This type of research takes many years to produce results because the children need to be followed throughout their lives. So it will be some time before we know the results of this research.

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Updated: 5 March 2015