Clinical relevance of bone marrow fibrosis and CD34-positive cell clusters in primary myelodysplastic syndrome

PURPOSE: We studied bone marrow (BM) histologic abnormalities in myelodysplastic syndromes (MDS) classified according to WHO criteria to determine their clinical correlates and prognostic value. PATIENTS AND METHODS: Three hundred one consecutive patients were retrospectively evaluated for BM fibrosis and CD34 immunoreactivity. Marrow fibrosis was assessed following the European consensus guidelines. RESULTS: Moderate to severe BM fibrosis was detected in 17% of cases and was associated with multilineage dysplasia (P = .001), high transfusion requirement (P < .001), and poor-risk cytogenetics (P = .007). CD34+ cell clusters were found in 23% of patients and were associated with WHO categories with excess of blasts (P < .001) and poor-risk cytogenetics (P = .001). In multivariable analysis, BM fibrosis and presence of CD34+ cell clusters had independent negative impact on overall survival (P < .001 and P = .019, respectively) and leukemia-free survival (P < .001 and P = .004, respectively). A hierarchical clustering analysis identified three subsets of patients with distinct clinical features. One cluster consisted mainly of patients with BM fibrosis, multilineage dysplasia, and high transfusion requirement; these individuals had lower overall survival and leukemia-free survival (P = .001 and P < .001, respectively). Within patients stratified according to International Prognostic Scoring System and WHO classification-based Prognostic Scoring System categories, BM fibrosis involved a shift to a one-step more advanced risk group. CONCLUSION: BM fibrosis identifies a distinct subgroup of MDS with multilineage dysplasia, high transfusion requirement, and poor prognosis and represents an independent prognostic factor that may be useful in clinical decision making. Furthermore, the presence of CD34+ cell clusters is an independent risk factor for progression to acute leukemia.