title: Mass-like extramedullary hematopoiesis: imaging features.
abstract: OBJECTIVE
  To report the imaging appearances of mass-like extramedullary hematopoiesis (EMH), to identify those features that are sufficiently characteristic to allow a confident diagnosis, and to recognize the clinical conditions associated with EMH and the relative incidence of mass-like disease.
  
  
  METHODS
  We retrospectively identified 44 patients with EMH; 12 of which (27%) had focal mass-like lesions and formed the study group. The study group consisted of 6 male and 6 female subjects with a mean age of 58 years (range 13-80 years). All 12 patients underwent CT imaging and 3 of the 12 patients had undergone additional MR imaging. The imaging characteristics of the extramedullary hematopoiesis lesions in the study group were analyzed and recorded. The patient's clinical presentation, including any condition associated with extramedullary hematopoiesis, was also recorded.
  
  
  RESULTS
  Ten of the 12 (83%) patients had one or more masses located along the axial skeleton. Of the 10 patients with axial masses, 9 (90%) had multiple masses and 7 (70%) demonstrated internal fat. Eight patients (80%) had paraspinal masses and 4 patients (40%) had presacral masses. Seven patients (70%) had splenomegaly. Eleven of the 12 patients had a clinical history available for review. A predisposing condition for extramedullary hematopoiesis was present in 10 patients and included various anemias (5 cases; 45%), myelofibrosis/myelodysplastic syndrome (4 cases; 36%), and marrow proliferative disorder (1 case; 9%). One patient had no known predisposing condition.
  
  
  CONCLUSIONS
  Mass-like extramedullary hematopoiesis most commonly presents as multiple, fat-containing lesions localized to the axial skeleton. When these imaging features are identified, extramedullary hematopoiesis should be strongly considered, particularly when occurring in the setting of a predisposing medical condition.
authors.affiliation: Synergy Radiology Associates, P.A., 7026 Old Katy Road #276, Houston, TX 77024, USA.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Ginzel
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Kransdorf
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Peterson
authors.forename: Hillary W
authors.initials: HW
authors.lastname: Garner
authors.forename: Mark D
authors.initials: MD
authors.lastname: Murphey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001859:Bone Neoplasms / Q000175:diagnosis*; D003240:Connective Tissue Diseases / Q000175:diagnosis*; D005260:Female; D006411:Hematopoiesis, Extramedullary; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult
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