Figure 1.

Prefibrotic PMF is associated with a hypercellular marrow characterized by the presence of increased numbers of hypolobulated megakaryocytes with atypical forms often present in clusters, increased granulopoiesis and decreased erythropoiesis (left). ET bone marrow is less cellular with largely unremarkable erythropoiesis and granulopoiesis (right). Megakaryopoiesis is increased with large hyperlobulated (staghorn-like) megakaryocytes.

(Top): republished with permission of American Society of Hematology. Permission conveyed through Copyright Clearance Center, Inc.¹¹