classification
Last reviewed 01/2018
In 1982 the French-American-British (FAB) group developed a classification system for myelodysplastic syndromes (MDS) according to morphological criteria:
SUB-TYPE DISTINGUISHING FEATURES IN MARROW Refractory anaemia < 5% blasts Refractory anaemia + ringed sideroblasts < 5% blasts; ringed sideroblasts > 15% Refractory anaemia + excess blasts 5-20% blasts Refractory anaemia + blasts in transformation 20-30% blasts Chronic myelomonocytic leukaemia blood monocytes > 1 x 10^9/l
The World Health Organisation (WHO) have produced a revised classification for MDS (1)
- in this classification system refractory anemia (RA) and sideroblastic anemia (RARS) have been more strictly defined, including only cases with a predominance of cell atypias in the erythroid lineage
- chronic myelomonocytic leukemia is reclassified under a separate category
- a new category refractory cytopenias with multilineage dysplasias (RCMD) has been defined as MDS presenting less than bone marrow (BM) blasts, but showing cell atypias in more than 10% in two or three hemopoietic cell lines
- the new classification also includes as a separate entity the 5q-syndrome
- a category "unclassified" has been created in order to include cases with peripheral cytopenias, discrete atypias in granulocytes and/or megakaryocytes and BM blasts lower than 5%
- in addition to the pathologic classification, various prognostic predictors were formatted into scoring systems. BM blast percentage, cytopenias, and cytogenetics are the backbone for those prognostic models. The International Prognostic Scoring System is a product of pooled data from previous scoring systems and a useful tool to predict survival and acute myelogenous leukemia evolution
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