AML megakaryoblastic leukemia

Bone marrow aspiration often results in a “dry tap”, due to the fibrosis.
Megakaryoblast are pleomorphic, usually larger then myeloblasts (12-20 µm), have a round to slightly indented nucleus with fine reticular chromatin and multiple nucleoli, often with abundant strong agranular basophilic cytoplasm, cytoplasmic blebs or pseudopods. They may appear in clusters mimicking metastatic tumors. In some cases the blasts can be smaller, with a high nuclear-cytoplasmic ratio and resemble lymfoblasts.
Peripheral blood smears show circulating micromegakaryocytes, megakaryocytic fragments, atypical giant platelets, and blasts.

They express CD41, CD61, CD36, often CD13 and/or CD33. CD34, HLA-Dr and CD45 are often negative.