Figure 2.

Primitive neuroectodermal tumors; location. Low magnification view of a JCPyV transgenic mouse brain demonstrating a small pocket of neoplastic cells (arrow) in the lower portion of the brainstem ((A) hematoxylin and eosin). T-Antigen immunolabeling highlights this small collection of neoplastic cells (100× magnification). (B). Full montage of a JCPyV transgenic mouse brain, demonstrating a large tumor, which substitutes the majority of the brain parenchyma (100× magnification). ((C) H & E). Consecutive full montages showing very small PNETs located in the brainstem ((D,E) H & E and T-Antigen respectively). At low magnification the small blue cell tumors in the medulla are evident (Panel F). These embryonal tumors can also reach large dimensions when located in the basal ganglia ((G,H) H & E and T-Antigen respectively). In very few cases the tumors originated in the olfactory bulb ((I) 100× magnification). Panels (J) and (K) depict the subarachnoid dissemination of these tumors in the cerebellum, typical of PNETs. Finally, very few cases de-veloped tumors in the spinal cord ((L) full montage, H & E and T-Antigen).