title: Onion skin.
abstract: Radiological terminology includes a number of interesting and often amusing terms intended to help us understand and remember the pathological abnormality being described. What radiological sign is illustrated in Fig. 1 and in what condition is it most frequently observed?
authors.affiliation: Children's Hospital, Birmingham.
authors.forename: S
authors.initials: S
authors.lastname: Chapman
mesh_terms: D001859:Bone Neoplasms / Q000000981:diagnostic imaging*; D006801:Humans; D010521:Periosteum / Q000000981:diagnostic imaging; D011859:Radiography; D012512:Sarcoma, Ewing / Q000000981:diagnostic imaging*; D009626:Terminology as Topic