Primitive Neuroectodermal Tumor

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There are two different tumor types, both of which are unfortunately referred to as primitive neuroectodermal tumors (PNET). These include "peripheral" PNET and "CNS" PNET. This can be a source of confusion.

The "peripheral" PNET is now thought to be virually identical to Ewing's sarcoma:

According to Robbins Pathologic Basis of Disease, 7th edition "Current evidence indicates that both Ewing sarcoma and PNET have a similar neural phenotype and, because they share an identical chromosome translocation, they should be viewed as the same tumor, differing only in their degree of neural differentiation. Tumors that demonstrate neural differentiation by light microscopy, immunohistochemistry, or electron microscopy have been traditionally labeled PNETs, and those that are undifferentiated by these analyses have been diagnosed as Ewing sarcoma."

The "CNS" PNET is often referred to as supratentorial PNET. Medulloblastoma and pinealoblastoma are very similar appearing tumors that occur in somewhat different CNS locations than supratentorial PNET. Medulloblastoma occurs in the cerebellum, while pinealoblastoma occurs in the pineal region.