title: Expression of CD99 in Multiple Myeloma: A Clinicopathologic and Immunohistochemical Study of 170 Cases.
abstract: BACKGROUND
  Multiple myeloma (MM) is a heterogeneous and ultimately fatal disease. Risk stratification using prognostic biomarkers is crucial to individualize treatments. We sought to investigate the role of CD99, a transmembrane protein highly expressed in many hematopoietic cells including subpopulations of normal and neoplastic plasma cells, for MM risk stratification.
  
  
  METHODS
  CD99 expression was measured in paraffin samples of bone marrow and extramedullary biopsies of 170 patients with MM. Patients were divided into those with high score (moderately and strongly positive) and low score (negative and weakly positive), with all staining being cytoplasmic and/or membranous.
  
  
  RESULTS
  High anti-CD99 immunostaining was observed in 72 of 136 (52.9%) bone marrow biopsies and 24 of 87 (27.6%) extramedullary biopsies in MM. High CD99 expression of extramedullary specimens was associated with significantly longer overall survival (OS; p=.016). High CD99 expression of extramedullary specimens was also associated with better prognosis in the nonautologous stem cell transplantation group of MM patients (p=.044). In multivariate analysis, International Staging System stage was an independent prognostic factor, whereas CD99 expression was no longer statistically significant.
  
  
  CONCLUSIONS
  Expression of CD99 in extramedullary specimens was correlated with longer OS, suggesting that CD99 may be a helpful immunohistochemical marker for risk stratification.
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Shin
authors.affiliation: Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hyangsin
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Geunyoung
authors.initials: G
authors.lastname: Jung
authors.affiliation: Cell Dysfunction Research Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Minchan
authors.initials: M
authors.lastname: Gil
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hosub
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Young Soo
authors.initials: YS
authors.lastname: Park
authors.affiliation: Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Dok Hyun
authors.initials: DH
authors.lastname: Yoon
authors.affiliation: Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Cheolwon
authors.initials: C
authors.lastname: Suh
authors.affiliation: Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Chan-Jeoung
authors.initials: CJ
authors.lastname: Park
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jooryung
authors.initials: J
authors.lastname: Huh
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. ; Cell Dysfunction Research Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Chan-Sik
authors.initials: CS
authors.lastname: Park
keywords: Autologous stem cell transplantation; CD99; Immunostaining; Multiple myeloma