title: MRI and clinical features of Langerhans cell histiocytosis (LCH) in the pelvis and extremities: can LCH really look like anything?
abstract: OBJECTIVE
  To assess clinical and MRI features of Langerhans cell histiocytosis in the pelvis and extremities.
  
  
  METHODS
  The MRI and clinical features of 21 pathologically proven cases of LCH involving the pelvis and extremities were studied. Multiple characteristics of the lesions were evaluated (location, size, T1/ T2/post-contrast features, perilesional bone and soft tissue signal, endosteal scalloping, periosteal reaction, soft tissue mass, pathologic fracture). Pre-biopsy radiologic diagnoses were collected from the original clinical reports. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), temperature, and white blood cell count (WBC) were collected at the time of diagnosis when available.
  
  
  RESULTS
  The locations of the LCH lesions included five humerus, four femur, five ilium, one tibia, one clavicle, and three scapula. Lesional size ranged from 1.8 to 7.1 cm, with a mean of 3.6 cm. All lesions demonstrated perilesional bone marrow edema, periosteal reaction, endosteal scalloping, and post-contrast enhancement. An associated soft tissue mass was present in 15/21 (71.4 %). Clinically, the WBC, ESR, and CRP were elevated in 2/14 (14 %), 8/12 (67 %), and 4/10 (40 %) of cases, respectively. Fever was documented in 1/15 (7 %) patients and pain was reported in 15/15 (100 %).
  
  
  CONCLUSIONS
  The clinical and radiologic features of LCH in the pelvis and extremities overlap with infection and malignancy, but LCH must be considered in the differential diagnosis, as it routinely presents with aggressive MRI features, including endosteal scalloping, periosteal reaction, perilesional edema, and a soft tissue mass. Furthermore, an unknown skeletal lesion at presentation without aggressive MRI features is unlikely to represent LCH.
authors.affiliation: Department of Medical Imaging, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, 225 E. Chicago Ave, Chicago, IL, 60611, USA. jsamet@luriechildrens.org.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Samet
authors.affiliation: Departments of Pediatrics, Division of Hematology/Oncology/Stem Cell Transplant, Ann & Robert H. Lurie Children's Hospital of Chicago, Northwestern University Feinberg School of Medicine, 225 E. Chicago Ave, Chicago, IL, 60611, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Weinstein
authors.affiliation: The Russell H. Morgan Department of Radiology & Radiological Science, The Johns Hopkins University School of Medicine, 601 North Wolfe Street, Baltimore, MD, 21287, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Fayad
mesh_terms: D000293:Adolescent; D000328:Adult; D001847:Bone Diseases / Q000000981:diagnostic imaging* / Q000473:pathology*; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005121:Extremities / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D006646:Histiocytosis, Langerhans-Cell / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010384:Pelvic Bones / Q000000981:diagnostic imaging / Q000473:pathology; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult
keywords: Extremities; LCH; Langerhans cell histiocytosis; MRI; Pediatric bone lesion; Pelvis