<prompt> Ewings sarcoma arises fromEndothelial cellsOsteocytesMesodermPrimitive neuroectodermal cells  <response>: Ans. d Primitive neuroectodermal cells. Ref. Robbin, Pathologic Basis of Diseases 5th833PNETs Ewings Sarcoma is the highly malignant primary bone neoplasm having specific cytogenetic analysis i.e. t 11,12, characterized by small round cells pseudo-rossets and is thought to be a primitive neuroectodermal tumor PNET with 75 patients being 20 years age and having male predilection. Other PNETs include- Medulloblastoma,- Pineoblastoma,- Neuroblastoma,- Askin tumor,- Retinoblastoma, etc. 