Primitive neuroectodermal tumors (PNET) Symptoms & Causes

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What exactly are PNET?  Are they the same as medulloblastomas?

Yes and no. Under a microscope, PNET tumors appear to be similar to a tumor called medulloblastoma, and some will classify medulloblastoma as "PNET (cerebellum)." However, it has been demonstrated that medulloblastomas behave differently than PNET in other locations in the brain.

According to the World Health Organization (WHO), all undifferentiated tumors—regardless of location—are derived from common cells and are therefore classified as PNET.  To differentiate, their location is frequently indicated in parentheses. This separates medulloblastoma (PNET cerebellum) and pineoblastoma (PNET in the pineal region) from other PNET such as PNET in the supratentorial compartment (meaning occurring in the cerebrum) or in the spine.

What causes a PNET?

Researchers have not been able to find an identifiable cause or risk factors for PNET. There doesn't appear to be a genetic predisposition, meaning the disease does not seem to run in families.

What are the symptoms of a PNET?

The symptoms of a PNET depend on the location of the tumor, and each child may experience symptoms differently.  Symptoms of a PNET in the supratentorial compartment usually arise quickly and last up to several weeks. These tumors are often seen in the older child or teenager.

Some common symptoms occur due to increased pressure within the brain, including:

Pineoblastomas (PNET in the pineal region, a tiny organ near the center of the brain) are usually seen in young children. Common symptoms may include increased pressure in the brain, resulting in:

  • headache (generally upon awakening in the morning)
  • vomiting
  • fatigue/lethargy
  • eye movement problems and/or complaints of double vision, since the tumor is close to the nuclei (centers in the brain) that regulate eye movements and coordination

Symptoms of PNET of the spine may include:

  • back and/or leg pain
  • slow development of weakness in the legs
  • impairment of bowel and/or bladder function, including incontinence

The symptoms of a PNET may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.

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