As of your SEM-image with equidensitic [pseudo-] coloration - demonstrating RBC's - the cell diameter should be approx. 14-15 times bigger (not considering possible shrinking artefacts from processing) than the RBC's.
Would it be possible to add either some measure bar or to tell us what the diameter of the cell (after SEM-Prep) really is / was?
Normal size of megakaryocytes [ cf. eg. http://www.ncbi.nlm.nih.gov/pubmed/7126866] usually is given to range from 10 - 65 µm, acc. to other sources up to 100 µm].