ULTRASTRUCTURAL OBSERVATIONS ON BONE-MARROW CELLS OF 26 PATIENTS WITHMYELODYSPLASTIC SYNDROMES

Bone marrow aspirates from 26 patients with myelodysplastic syndrome ( MDS) were examined using transmission electron microscopy. The red blo od cell precursors in 9 patients showed Varying degrees of dyserythrop oiesis including the presence of 2 or more nuclei, nuclei with bizarre shape and iron deposits in the mitochondria. The myeloid series showe d a tendency to hypogranulation (5 patients) and in 2 patients there w ere signs of platelet phagocytosis. The monocytes had a normal ultrast ructure except for one patient with chronic myelomonocytic leukemia (C MML) with transformation to acute myelo-monocytic leukemia (AMML). In this case, the monocytes were immature, with markedly convoluted nucle i and scanty heterochromatin. The lymphocytes also had a normal appear ance, except for one patient in whom the lymphocytes were immature, wi th lobulated nuclei and suggested transformation of MDS to acute lymph oblastic leukemia. The plasma cells in 3 patients were slightly increa sed in number and in one of them Russell bodies were seen both in the cytoplasm and the nucleus. The megakaryocytic series showed a shift to the left and in one patient there were signs of emperipolesis. The al terations in the hematopoietic cells in patients with MDS described in the present study indicate that the electron microscope may supplemen t light microscopic findings and help in the establishment of a correc t diagnosis. This may be also evident in those cases of MDS in which t he very early stages of leukemic transformation cannot be easily detec ted by light microscopy.