4 year old female child came with history of mass in the right side of the head in parietal region. CT scan shows large heterogenously enhancing soft tissue mass lesion seen in both intra and extracranial regions, the intracranial component is extradural causing mass effect on the right cerebellar hemisphere. There is bone erosion of right parietal bone.
MRI of the same patient T2 WI showing similar findings with large extra and intracranial components. There is complete involvement of the right parietal bone. Biopsy proved to be PNET.
Primitive Neuroectodermal Tumor (PNET) is a soft tissue sarcoma classically described under small round blue cell tumors (SRBCT). Synonyms include : PNET, Peripheral neuroepithelioma, Peripheal neuroblastoma, Askin tumor (Thoracopulmonary PNET) and Extraosseous Ewing's sarcoma. The incidence is 1% of the sarcomas. They often (75%) occure in the age of less than 35 years. Most investigators now believe that Ewing's sarcoma and PNET are different morphological expressions of one tumor type. In general, Ewing's sarcoma arises within the bone while PNET arises within soft tissues. PNET arising from the dura or skull vault is very rare and in this case it is diffucult to predict the origin of the tumor.Radiograph is often the first investigation to be done. CT and MRI are the investigations of choice to see for the extent of the lesion. MRI is preferred over CT scan. These can be used to look for the response to chemo and radiotherapy.Here is the link to the PNET at various sites:
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