Pediatric surgical image Lipofibromatosis of the knee in a 19-month-old child Sílvia Costa Dias a, ⁎ , Kieran McHugh a , Neil J. Sebire b , Neil Bulstrode c , Mary Glover d , Antony Michalski e a Department of Radiology, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom b Department of Pathology, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom c Department of Plastic Surgery, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom d Department of Dermatology, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom e Department of Oncology, Great Ormond Street Hospital for Children, London WC1N 3JH, United Kingdom Received 1 November 2011; revised 30 January 2012; accepted 20 February 2012 Key words: Lipofibromatosis; MRI Abstract Lipofibromatosis is a rare benign fibrofatty tumor of childhood. The typical presentation of this tumor is as a poorly demarcated and slow-growing mass involving the subcutaneous or deep soft tissues. Lipofibromatosis was first described in 2000, and since then, a small number of cases have been reported in the literature. We report a case of a 19-month-old boy who presented with a swelling of the anterior aspect of the right knee since birth, which had increased in size out of proportion with his growth. Magnetic resonance imaging was extremely useful because it showed the lipomatous nature of the mass, narrowing the differential diagnosis to the pediatric fibrofatty soft tissue tumors. The histologic biopsy revealed the specific diagnosis of lipofibromatosis. We describe the radiologic and pathologic features of this entity and discuss the differential diagnosis in a young child with a fat-containing limb mass. © 2012 Elsevier Inc. All rights reserved. Lipofibromatosis (LF) is a histologically distinct fibrofatty tumor of childhood, classically found in the distal extremities. Lipofibromatosis was formerly designated as infantile fibromatosis of nondesmoid type [1]. Fetsch et al [2] recently first characterized this tumor as a separate entity, which is largely composed of adipose tissue traversed by bundles of spindled fibroblastic-like cells. The published literature emphasizes the histopathology features, with very limited documentation of the imaging findings of this rare tumor. The magnetic resonance imaging (MRI) findings are not com- pletely specific; however, there is a good correlation with histopathology features [3]. These findings are described and illustrated in this case report of LF, and the differential diagnosis of this entity is also discussed. 1. Case report A 19-month-old boy presented with a swelling of the anterior aspect of the right knee since birth, which initially measured 3 × 3 cm. The lesion grew during the first year of life enlarging out of proportion with his growth. On physical examination, there was a smooth mass with slightly increased hair growth on the anterior aspect of the right knee (Fig. 1). He had full range of movement at the knee with no limitation of function and no tenderness. The re- mainder of the physical examination was unremarkable. ⁎ Corresponding author. Rua Eugénio de Castro 170, Habitação 91, 4100-225 Porto, Portugal. Tel.: +351915301643; fax: +351225432869. E-mail address: silviacostadias@hotmail.com (S. Costa Dias). www.elsevier.com/locate/jpedsurg 0022-3468/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2012.02.009 Journal of Pediatric Surgery (2012) 47, 1028–1031