What is primitive neuroectodermal tumour (PNET)?

This page tells you about primitive neuroectodermal tumours (PNET). There is information about

What PNET is
PNETs of the brain or spinal cord
Peripheral PNETs
Treatment of soft tissue Ewing's sarcoma

Research into PNETs
Side effects of treatment
Possible long term side effects
Research into long term side effects

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 from the earliest stages of a baby’s development in the womb. 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)

Primitive neuroectodermal tumours that occur in the brain and spinal cord (the central nervous system or CNS) include

Medulloblastoma (develops in the back part of the brain – the hindbrain)
Pineoblastoma (develops in the pineal region of the brain)
Non pineal supratententorial PNET (develops in the upper part of the brain)

Medulloblastoma is the most common of these. You can find information about treating primitive neuroectodermal tumours in the treating brain tumours section.

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.

Treatment for soft tissue Ewing's sarcoma usually involves a combination of surgery, chemotherapy and radiotherapy. But the specific treatment you need will depend on

The type of PNET
The position of the tumour in your body
The size of the tumour
Whether the tumour has spread to other parts of the body
Your age and general health (these tumours are more common in children)

Doctors are researching new ways of treating primitive neuroectodermal tumours. Several trials are taking place at the moment. To find out more about these trials, go to our clinical trials database and type ‘PNET’ into the advanced search box. You can find information about treatment for Ewings’s sarcoma of the bone in our bone cancer section.

All treatments have side effects. These usually happen when your child is having treatment or very soon afterwards. There are medicines to help control most of these immediate side effects so tell your child’s doctor if they 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. 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 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 effects of treatment include

Fertility problems
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 child’s doctor will talk to you about the possible risks depending on the treatment your child has had. They will continue to keep a close eye on your child so that any problems can be treated early.

The Scottish Intercollegiate Guidelines Network (SIGN) and the National Institute for Health and Clinical 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) have also produced information about long term follow up to guide doctors on how best to do this.

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 sometime before we know the results of this research.