Myelodysplastic Syndrome: Morphological Aspects of Dysmyelopoiesis

Abstract

Ninety-nine patients with myelodysplastic syndrome (MDS) were analysed to determine the significance of morphological aspects of dysmyelopoiesis and the affects of dysmyelopoiesis on prognosis. For subtyping MDS, FAB criteria (Bennett et al. 1982) was applied. For refractory anemia (RA) the following diagnostic criteria was used: persistent unexplained anemia with Hb concentration less than 11 g/dl and normo-or hyper-cellular marrow. Obeying FAB criteria, the following morphological abnormalities were evaluated to represent dysmyelopoiesis: ‘dyserythropoiesis’ (megaloblastic changes, multinuclearity, abnormalities in the nuclear shape, nuclear fragments, ring sideroblasts), ‘dysgranulopoiesis’ (Pelgar-Huet type nuclei, markedly hypogranular PMN, ring nuclei, hypersegmentation of 6 or more segments), and ‘dysmegakaryopoiesis’ (micromegakaryocytes, round mononuclear megakaryocytes and megakaryocytes with separated multiple nuclei). Two hundred erythroblasts, 200 granulocytes and 25, if possible, megakaryocytes were counted and the results were reported as percentages of cells showing abnomalities, In order to determine whether the dysplastic changes are specific to MDS or not, we also examined the bone marrows from normal subjects and patients with autoimmune hemolytic anemia (AIHA), iron deficiency anemia (IDA), and aplastic anemia (AA). The following results were obtained:
1) The number of patients with MDS subtypes was as follows: RA 49, RA with ring sideroblasts 5, RA with excess of blasts (RAEB) 20, RAEB in transformation (RAEB in T) 22, MDS with myelofibrosis 3.
2) The rates of leukemic transformation were 12.2%, 40.0%, 55.0% in RA, RAEB, RAEBin T respectively.
3) The analysis of Kaplan-Meier survival curves revealed that the patients with RA had good prognosis and the patients with RAEB or RAEB in T had bad prognosis. The 50% survival of RAEB and RAEB in T were 12.5 and 14.3 months respectively.
4) Slight degree of dyserythropoesis or dysmegakaryopoiesis was occasional seen in a minority of normal subjects and some patients with IDA or AA, but dysgranulopoiesis was only seen in the patients with MDS.
5) The analysis of Kaplan-Meier survival curves revealed the presence of dysmyelopoiesis (>5% dyserythroblasts, >5% dysmegakaryocytes, ≥0.5% dysgranulocytes) to be a sign of bad prognosis.
6) The complication of myelofibrosis in patients with MDS made duration of survival very short. All patients terminated in acute leukemia, in which some leukemic cells were identified as megakaryoblasts.
7) Two cases of typical aplastic anemia were turned to MDS with cellular marrow and dysgranulopoiesis.
8) RA consists of a wide range of disease from cases indistinguishable form mild AA to cases close to RAEB.