Medulloblastomas are Primitive NeuroEctodermal Tumors (PNETs) that occur in the posterior fossa.
PNETs that occur elsewhere in the brain - above the tentorium are called supratentorial primitive neuro-ectodermal tumors.
These tumors have a worse outlook than medulloblastomas and are always placed in a high risk category - even if there is no metastatic disease at presentation.
Standard treatment therefore in a child aged 5 years or more for a supratentorial PNET would be craniospinal RT (3600 cGy in 180 cGy fraction size) - followed by a boost to the primary tumor to a total of 5580 cGy or 5400 cGy. Concurrent combination chemotherapy would also be given as per a high risk medulloblastoma protocol.
Below is a MR image of a large supratentorial PNET (#1) in a 6 year old girl. The tumor is compressing the lateral ventricle and associated with some midline shift.
Here is the same tumor (sagital view)
