Proposals for a Grading System for Diagnostic Accuracy of Myelodysplastic Syndromes

Despite recent advances in cytogenetics and molecular research, universal biomarkers for the diagnosis of the myelodysplastic syndromes (MDS) are still lacking. It is not easy to diagnose MDS by morphology alone, particularly in patients with < 5% blasts in the bone marrow (BM) and normal karyotype. Therefore, the possibility of misdiagnosis and discordance among observers can occur. In order to resolve these problems, we propose a grading system for diagnostic accuracy of MDS. The diagnostic accuracy of MDS is graded into “definite,” “probable,” or “possible” in addition to “idiopathic cytopenia(s) of uncertain significance (ICUS).” The criteria of grading for diagnostic accuracy are a combination of (1) the frequency of blasts in BM, (2) grade of dysplasia (high, intermediate, or low), and (3) division of cytogenetics (abnormal, normal, or unknown). For quantitative morphologic evaluation of dysplasias, we classified morphologic dysplastic changes into highly specific category A (pseudo–Pelger-Huet anomaly, degranulation of neutrophils, micromegakaryocytes, and ringed sideroblasts) and less specific category B (dysplasias other than those in category A). We believe that diagnostic problems would be reduced by using our grading system and repeating BM examination at suitable intervals for patients who are allocated into the “possible” or “ICUS” categories, and this will make the vague margin of MDS category clearer.