Presentation with myelofibrotic transformation of previously undiagnosed ET. (A) Platelet and hemoglobin levels during a 10-year period before presentation with PMF in a patient at the age of 67 years; a marked thrombocytosis between 8 and 10 years before diagnosis is followed by a gradual decrease in platelet count and progressive anemia in the absence of iron deficiency or inflammation. (B) At clinical presentation, left, Wright-Geimsa–stained blood film showing leukoerythroblastosis and tear-drop red cells; middle, hematoxylin and eosin–stained bone marrow trephine biopsy showing clusters of dysplastic megakaryocytes; and right, silver-stained bone marrow trephine biopsy showing grade 4 reticulin fibrosis (on 0-4 scale). Red and blue shaded areas represent the normal range for hemoglobin and platelet count, respectively.