Morphologically, apoptosis was seen in all the lineages, with a predominance in the myeloid and erythroid lineages.

(A) Semithin section of LDF from MDS patient showing minimal apoptosis (toluidine blue staining, original magnification × 400). (B) Electron micrograph of semithin section A (uranyl acetate and lead citrate, original magnification × 6600). (C) Semithin section of HDF from MDS patient showing increased apoptosis in the myeloid and erythroid lineage (toluidine blue staining, original magnification × 400). (D) Electron micrograph of semithin section C. Note the characteristic appearance of apoptosis, segregation of the chromatin in sharply circumscribed masses that lie against the nuclear envelope and condensed cytoplasm (uranyl acetate and lead citrate, original magnification × 6600). (E-H) Ultrastructural features of nonapoptotic cells in MDS. (E) Note the myeloblast with euchromatin nucleus, nucleoli, and a fair number of primary and secondary granules. (F) Dysplastic promyelocyte showing a low nuclear cytoplasmic ratio and abundant granules with Auer rods. (G) As the cell matures, note the characteristic Pelger-Huet anomaly showing bilobed neutrophil. (H) Polychromatophilic megaloblast with the appearance of a few clumps among the chromatin beads (uranyl citrate, original magnification × 5000). (I-L) Ultrastructural features of apoptotic cells in MDS. (I) A myeloblast showing the early stages of apotosis with only marginal condensation of nuclear chromatin, with a prominent nucleoli and preservation of the integrity of the organelles (original magnification × 8300). (J) Apoptotic promyelocyte with a perinuclear vacuole (original magnification × 6600). (K) Mature granulocytic neutrophil undergoing apoptosis, showing nuclear budding (original magnification × 8300). (L) Apoptotic erythroid cell (uranyl acetate and lead citrate, original magnification × 6600).