title: Can sarcoidosis and metastatic bone lesions be reliably differentiated on routine MRI?
abstract: OBJECTIVE
  Sarcoidosis lesions revealed on MRI in the axial skeleton and long bones resemble osseous metastases, which can lead to a potentially significant misdiagnosis. We hypothesized that osseous sarcoidosis lesions could be differentiated from osseous metastases on MRI and sought to propose and evaluate features distinguishing these entities.
  
  
  METHODS
  MR images obtained at 1.5 T of 34 subjects (22 with osseous metastatic disease, 12 with osseous sarcoidosis) with 79 single or multiple bone lesions (40 metastatic, 39 sarcoidal) were reviewed independently by two blinded, experienced musculoskeletal radiologists. Fluid-sensitive and T1-weighted images were viewed separately. Proposed discriminating features were peri- or intralesional fat, specified border characteristics, and the presence of an extraosseous soft-tissue mass. An additional feature for spinal lesions was posterior element involvement. On the basis of these criteria, the readers provided a binary diagnosis and confidence score.
  
  
  RESULTS
  The overall sensitivity for both readers was 46.3% and specificity, 97.4%. T1-weighted images were associated with higher sensitivity than T2-weighted images (59.0% vs 34.1%, respectively; p = 0.025) and with comparable specificity (97.6% vs 97.2%, p = 0.91). Diagnostic accuracy was higher using the discriminators of a mass or posterior element involvement for metastasis (83.3%) than border characteristics (68.0%) or lesion fat (65.0%) for sarcoidosis; the latter two features provided near 100% specificity but poor sensitivity (14.3% and 0%, respectively). Readers reported higher confidence diagnosing osseous sarcoidosis lesions than metastatic lesions, with a trend for higher confidence with T1-weighted images (p = 0.088).
  
  
  CONCLUSIONS
  Osseous sarcoidosis lesions cannot be reliably distinguished from metastatic lesions on routine MRI studies by readers experienced in evaluating these lesions.
authors.affiliation: Department of Radiology, NYU Langone Medical Center Hospital for Joint Diseases, New York, NY 10016, USA. sandra.moore@nyumc.org
authors.forename: Sandra Leigh
authors.initials: SL
authors.lastname: Moore
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Kransdorf
authors.forename: Mark E
authors.initials: ME
authors.lastname: Schweitzer
authors.forename: Mark D
authors.initials: MD
authors.lastname: Murphey
authors.forename: James S
authors.initials: JS
authors.lastname: Babb
mesh_terms: D000328:Adult; D001847:Bone Diseases / Q000175:diagnosis*; D001859:Bone Neoplasms / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D016015:Logistic Models; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012507:Sarcoidosis / Q000175:diagnosis*; D012680:Sensitivity and Specificity