Received: 27 June 2002 Revised: 26 November 2002 Accepted: 3 December 2002 Published online: 12 March 2003 © ISS 2003 Abstract Objective: To identify the common imaging features of intra- osseous lipomas on radiographs, magnetic resonance imaging (MRI) and computed tomography (CT), and review their histological fea- tures. Design and patients: Thirty- five previously unreported cases of intraosseous lipoma were reviewed and a meta-analysis was performed of another 110 cases identified from the English language literature. Results: The mean age at presenta- tion is 43 years. Sex distribution is nearly equal. Lipomas occur most frequently in the lower limb (71% overall), particularly in the os calcis (32%). Other common sites include the metaphyses of long bones, where lesions are typically eccentric. Lipo- mas are usually well defined, but marginal sclerosis is commoner in lesions of the os calcis (61%) than at other sites (38%). Calcification is also more frequent in the os calcis (62%), and almost invariably cen- trally located. Calcification at other sites is less common (30%), and is more variable in appearance. Bone expansion is less common (30%), and usually minimal. Fat ne- crosis and cyst formation identified on MRI is common (67%), and more frequent in the os calcis. Conclusions: Although there is cor- relation between the histological and radiological features of intraosseous lipomas in general, some discrepan- cies occur in the radiological ap- pearances of lipomas in different sites. The evidence that these lesions are true benign tumours of fat is controversial. Several aetiological factors have been implicated in their development. The constant location of os calcis lesions at the critical an- gle suggests an aetiology that may be related to biomechanical lines of stress. In other instances it is possi- ble that involution of pre-existing lesions may lead to the development of lipomas. Keywords Lipoma · Intraosseous · Intramedullary · Magnetic resonance imaging · Computed tomography Skeletal Radiol (2003) 32:209–222 DOI 10.1007/s00256-002-0616-7 A RT I C L E R. S. D. Campbell A. J. Grainger D. C. Mangham I. Beggs J. Teh A. M. Davies Intraosseous lipoma: report of 35 new case and a review of the literature Introduction Intraosseous lipoma was first described in 1880 [1], and is often considered to be one of the rarest primary bone tumours. It is composed of mature fat cells with vari- able small quantities of fibrous and vascular tissue [2, 3, 4, 5, 6, 7, 8]. Lipomas may undergo varying degrees of involution, with areas of fat necrosis, cyst formation and dystrophic calcification [5]. In this respect a lipoma may resemble a bone infarct at surgical resection and o histological examination. Carefulradiological-patho- logical correlation is required to avoid misinterpretatio [5, 9]. Radiographic diagnosis of a lipoma may not be straightforward. The differential diagnosis may inclu non-ossifying fibroma, aneurysmal bone cyst, simple cyst, fibrous dysplasia, giant cell tumour, bone infa and even chondroid tumours [2, 9, 10, 11, 12, 13, R. S. D. Campbell ( ✉ ) Department of Radiology, The James Cook University Hospital, Marton Road, Middlesbrough, TS4 3BW, UK e-mail: rob.campbell@stees.nhs.uk A. J. Grainger Department of Radiology, Leeds General Infirmary, Leeds, LS1 3EX, UK D. C. Mangham Department of Pathology, Royal Orthopaedic Hospital, Woodlands, Birmingham, B31 2AP, UK I. Beggs Department of Radiology, Royal Infirmary, Edinburgh, Scotland, EH3 9YW, UK J. Teh Department of Radiology, Nuffield Orthopaedic Centre, Headington, Oxford, OX3 7LD, UK A. M. Davies Department of Radiology, Royal Orthopaedic Hospital, Woodlands, Birmingham, B31 2AP, UK