Understanding the radiology of intracranial primitive neuroectodermal tumors from a pathological perspective: a review.

The concept of primitive neuroectodermal tumors (PNETs) has been controversial since its introduction in 1973. Understanding these tumors is important for the neuroradiologist, because certain radiological features may suggest their diagnosis. A review of the PNET concept, as well as the different types of intracranial PNETs is made, using as a framework the cytogenesis of the brain. Emphasis is given to pathologic features, as they ultimately determine radiologic findings. Supratentorial PNETs are large, bulky, heterogeneous masses with "cystic" (necrotic) areas, calcification, and very little edema. Infratentorial PNETs are generally less heterogeneous, but the larger tumors tend to be more cystic, necrotic, and calcific, resembling supratentorial PNETs.