Polycythemia. Histological features of chronic myeloproliferative neoplasmsA & B: Polycythemia Vera - Hypercellular bone marrow with increased numbers of erythroblasts and pleomorphic megakaryocytes (A:hematoxylin and eosin - magnification 200 x). Megakaryocytes show hyperlobated nuclei and are arranged in loose clusters (B: hematoxylin and eosin - magnification 1000 x)C & D: Essential thrombocythemia - No significant alterations of the myeloid and erythroid series. Megakaryocytes are significantly increased in number, show hyperlobated nuclei and are isolated or arranged in loose clusters (C: hematoxylin and eosin - magnification 1000 x). Reticulin fibers are present in a loose network with some intersections (D: Gomori argentic impregnation - 1000 x)Philadelphia-negative chronic myeloproliferative neoplasms. Bittencourt RI, Vassallo J, Chauffaille Mde L, Xavier SG, Pagnano KB, Nascimento AC, De Souza CA, Chiattone CS - Revista brasileira de hematologia e hemoterapia (2012). Not Altered. CC.