title: Imaging of peripheral PNET: common and uncommon locations.
abstract: OBJECTIVE
  We present the imaging features of peripheral primitive neuroectodermal tumour (PNET) in eight children, highlighting the unusual locations of this tumour in three children.
  
  
  METHODS
  At presentation, the tumours were studied with magnetic resonance imaging (MRI; n = 6), computed tomography (CT; n = 7) and ultrasound (US; n = 1). The diagnoses were confirmed histologically (n = 8), immunohistochemically (n = 8), by cytogenetics (n = 3) and electron microscopy (n = 1). Correlation with gross pathology, histology, treatment and outcome were obtained.
  
  
  RESULTS
  The tumours were located in the chest wall (n = 2), shoulder, pelvis, small bowel mesentery, adrenal gland, dura mater and skin and subcutaneous tissue of the abdominal wall (n = 1 each). Peripheral PNET arising from the small bowel mesentery, adrenal gland and dura mater have not been previously reported in the English literature. The tumours were mainly large (mean size: 10.6 cm) and infiltrative. All tumours were heterogeneously hyperintense on T2-weighted MRI, heterogeneously iso/hypodense on CT and had variable contrast enhancement. Most tumours were heterogeneously hypointense to muscle on T1-weighted MRI. US showed a hypoechoic mass with a cystic component.
  
  
  CONCLUSIONS
  Peripheral PNET can occur in unusual locations. The clinical and imaging features of peripheral PNET are non-specific, making tissue diagnosis essential. PNET should be included in the differential diagnosis of aggressive soft tissue tumours in children.
authors.affiliation: Department of Diagnostic Radiology, The University of Hong Kong, Queen Mary Hospital, Hong Kong. plkhong@hkucc.hku.hk
authors.forename: P L
authors.initials: PL
authors.lastname: Khong
authors.forename: G C F
authors.initials: GC
authors.lastname: Chan
authors.forename: T W H
authors.initials: TW
authors.lastname: Shek
authors.forename: P K H
authors.initials: PK
authors.lastname: Tam
authors.forename: F L
authors.initials: FL
authors.lastname: Chan
mesh_terms: D000293:Adolescent; D000310:Adrenal Gland Neoplasms / Q000175:diagnosis; D002648:Child; D002675:Child, Preschool; D004388:Dura Mater; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000175:diagnosis; D008643:Mesentery; D018242:Neuroectodermal Tumors, Primitive / Q000175:diagnosis*; D010534:Peritoneal Neoplasms / Q000175:diagnosis; D012983:Soft Tissue Neoplasms / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed