title: MR imaging of simple bone cysts in children: not so simple.
abstract: OBJECTIVE
  The unicameral bone cyst (UBC) is a common cystic bone lesion seen in children. We review and summarize its MR findings, focusing on their appearance following contrast enhancement, and correlating them to known histologic features of UBC.
  
  
  METHODS
  A retrospective review of 20 cases (13 boys, 7 girls; age range, 1-17 years; mean age, 8.9) diagnosed as UBC was conducted. Clinical histories, radiographic and MR features, follow-up data, and available pathologic findings were noted.
  
  
  RESULTS
  At initial presentation 18 (90 %) of the patients with UBC had a history of acute or remote pathologic fracture. Cysts with history of fracture displayed heterogeneous fluid signals on T1-(n = 9, 50%), and T2-weighted (n = 15, 83 %) MR images. Gadolinium-enhanced images were obtained in 15 of the 18 UBC cases with history of previous fracture. All showed enhancement with focal, thick peripheral, heterogeneous, or subcortical patterns. Focal nodules of homogeneous enhancement (diameter > 1 cm) within the UBC (n = 5) correlated with areas of ground-glass opacification on plain film. Other interesting MR features were fluid-fluid levels (n = 11), "fallen-leaf" sign (n = 1), soft-tissue changes (n = 2), and detection of septations not seen on plain film (n = 2).
  
  
  CONCLUSIONS
  UBCs frequently appear complicated on MR imaging, with heterogeneous fluid signals and regions of nodular and thick peripheral enhancement related to previous pathologic fracture and early healing.
authors.affiliation: Department of Diagnostic Imaging, The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Margau
authors.forename: P
authors.initials: P
authors.lastname: Babyn
authors.forename: W
authors.initials: W
authors.lastname: Cole
authors.forename: C
authors.initials: C
authors.lastname: Smith
authors.forename: F
authors.initials: F
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001845:Bone Cysts / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy; D001842:Bone and Bones / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D005598:Fractures, Spontaneous / Q000175:diagnosis; D005682:Gadolinium; D006801:Humans; D007089:Image Enhancement; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D011859:Radiography; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D005682:Gadolinium