Primitive Neuroectodermal Tumor, a Rare Cause of Musculoskeletal Manifestations in a Child

Among small blue round cell tumors, primitive neuroectodermal tumors (PNETs) are a group of Ewing sarcoma family of tumors that are highly aggressive, poorly differentiated and form a group of tumors defined by their appearance that are thought to derive from postganglionic parasympathetic primordial cells located throughout the parasympathetic autonomic nervous system. Batsakis et al divided PNET family of tumors into the following 3 groups based on the tissue of origin: peripheral PNET, CNS PNET and neuroblastoma[1]. The peripheral PNET (pPNET) is now thought to be identical to Ewing family of tumors (EFTs). Tumors that demonstrate neural differentiation by light microscopy, immunohistochemistry, or electron microscopy have been traditionally called PNETs, and those that are undifferentiated by these analyses have been diagnosed as Ewing’s sarcoma[2]. Among the cPNET’s are medulloblastoma, pineoblastoma, cerebral neuroblastoma, ependymoblastoma, medulloepithelioma, primary rhabdomyosarcoma, and atypical teratoid/rhabdoid tumor[2]. Although these tumors are exceedingly rare, the annual incidence of tumors from birth to age 20 years is 2.9 per million population. In most large series published to date, pPNETs usually present in the second decade of life, with a slight male predilection. They account for 4-17% of all pediatric soft tissue tumors[3]