Myelofibrosis in primary myelodysplastic syndromes: clinical and biological significance.

In a retrospective study of 236 patients with primary myelodysplastic syndromes (MDS), 130 cases (55.1%) revealed myelofibrosis in bone marrow biopsies. It was observed that fibrosis mostly occurs focally or patchy, and collagen deposits were found very rarely (only four patients). The histopathology of bone marrow biopsies revealed several differences between fibrotic and non-fibrotic MDS: cellularity is significantly higher, dysmegakaryopoiesis is more pronounced, plasmocytes and mast cells are more often increased, and disturbance of marrow topography (particularly of the MK- and G-line) can be found more frequently in MDS with myelofibrosis. Reticulin fibrosis occurred in all subtypes of MDS; however, there was a higher incidence in chronic myelomonocytic leukemia. The frequency of abnormal growth of GM-progenitors was significantly higher in the MDS cases with myelofibrosis, compared to the cases without fibrosis. Clinical data showed significantly higher WBC, more frequent presence of immature granulocytes, and higher percentage of myeloblasts in peripheral blood and bone marrow in MDS with myelofibrosis compared to cases without myelofibrosis. Life expectancy was reduced to 13 mo, compared with 35 mo in MDS without fibrosis (p=0.00055). Time to leukemic transformation was 32 mo in MDS with fibrosis, compared with >56 mo in MDS without fibrosis (p=0.015). Myelofibrosis therefore seems to herald a poor prognosis.