Peripheral primitive neuroectodermal tumors (pPNET) are one of several of tumors with similar histology, composed of relatively uniform primitive small round blue cells.  They tend to be large and aggressive retroperitoneal tumors and share many demographic, radiographic and clinical similarities.

This case is also about the importance of clinico-radiological correlation and not being distracted by 'red herrings'.  In this case the nature of the trauma in a young patient not correlating with the extent of what was a presumed hematoma on the initial MRI.