The term primitive neuroectodermal tumor or PNET is a relatively new term that is used to describe a group of tumors. In these tumors, the type of cell seen is very similar. Their locations are quite different. Tumors that fall under the heading PNET include medulloblastoma (the most common), pineoblastoma, ependymoblastoma, retinoblastoma, neuroblastoma and esthesioneuroblastoma. Other than the medulloblastoma, these are all rare tumors. These tumors generally occur in children.
SYMPTOMS
The symptoms of the PNET group of tumors are related to their size and location. Commonly, they cause increased pressure inside the head. This can result in headache, nausea and vomiting. Other symptoms result from pressure on the brain itself and can result in weakness, visual problems and loss of balance. Seizures are common.
DIAGNOSIS
As always, the first steps in diagnosis are a careful history and physical examination. CT or MRI scanning performed without and with intravenous contrast enhancement are the next step. Because of the possibility of spread through the spinal fluid, MRI of the entire spine is frequently performed.
TREATMENT
Surgery is the usual first treatment for these tumors. They are generally unable to be cured by surgery. Further treatment with radiation therapy is the usual next step. For children under the age of three years, chemotherapy may be given instead of radiation therapy. Chemotherapy may also be used as additional treatment in older patients.