title: Bone cysts: unicameral and aneurysmal bone cyst.
abstract: Simple and aneurysmal bone cysts are benign lytic bone lesions, usually encountered in children and adolescents. Simple bone cyst is a cystic, fluid-filled lesion, which may be unicameral (UBC) or partially separated. UBC can involve all bones, but usually the long bone metaphysis and otherwise primarily the proximal humerus and proximal femur. The classic aneurysmal bone cyst (ABC) is an expansive and hemorrhagic tumor, usually showing characteristic translocation. About 30% of ABCs are secondary, without translocation; they occur in reaction to another, usually benign, bone lesion. ABCs are metaphyseal, excentric, bulging, fluid-filled and multicameral, and may develop in all bones of the skeleton. On MRI, the fluid level is evocative. It is mandatory to distinguish ABC from UBC, as prognosis and treatment are different. UBCs resolve spontaneously between adolescence and adulthood; the main concern is the risk of pathologic fracture. Treatment in non-threatening forms consists in intracystic injection of methylprednisolone. When there is a risk of fracture, especially of the femoral neck, surgery with curettage, filling with bone substitute or graft and osteosynthesis may be required. ABCs are potentially more aggressive, with a risk of bone destruction. Diagnosis must systematically be confirmed by biopsy, identifying soft-tissue parts, as telangiectatic sarcoma can mimic ABC. Intra-lesional sclerotherapy with alcohol is an effective treatment. In spinal ABC and in aggressive lesions with a risk of fracture, surgical treatment should be preferred, possibly after preoperative embolization. The risk of malignant transformation is very low, except in case of radiation therapy.
authors.affiliation: Clinique Arago, 93, boulevard Arago, 75014 Paris, France; Service de chirurgie orthopédique, hôpital Necker, 149, rue de Sèvres, 75015 Paris, France; Département de pédiatrie, institut Gustave-Roussy, 94805 Villejuif cedex, France. Electronic address: eric.mascard@wanadoo.fr.
authors.forename: E
authors.initials: E
authors.lastname: Mascard
authors.affiliation: Clinique Arago, 93, boulevard Arago, 75014 Paris, France; Service d'anatomopathologie, institut universitaire du cancer de Toulouse oncopole, Toulouse, France.
authors.forename: A
authors.initials: A
authors.lastname: Gomez-Brouchet
authors.affiliation: Clinique Arago, 93, boulevard Arago, 75014 Paris, France; Service de radiologie pédiatrique, hôpital Necker-Enfants-Malades, 149, rue de Sèvres, 75015 Paris, France.
authors.forename: K
authors.initials: K
authors.lastname: Lambot
mesh_terms: D000293:Adolescent; D001706:Biopsy; D001845:Bone Cysts / Q000175:diagnosis* / Q000628:therapy*; D017824:Bone Cysts, Aneurysmal / Q000175:diagnosis* / Q000628:therapy*; D002648:Child; D005260:Female; D005598:Fractures, Spontaneous / Q000453:epidemiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011379:Prognosis; D012307:Risk Factors; D016896:Treatment Outcome; D055815:Young Adult
keywords: Aneurysmal bone cyst; Biopsy; Bone tumor; Curettage; Simple bone cyst; Unicameral bone cyst