Anagrelide does not exert a myelodysplastic effect on megakaryopoiesis: a comparative immunohistochemical and morphometric study with hydroxyurea.

A comparative immunohistochemical and morphometric study was performed on megakaryocytes in 20 patients presenting with initial-early stage chronic idiopathic myelofibrosis and accompanying thrombocythemia to elucidate histological features developing after hydroxyurea (HU) versus anagrelide (ANA) therapy. Representative pre-and posttreatment bone marrow biopsies were involved including the monoclonal antibody CD61 for the identification of precursor and mature stages of megakaryopoiesis. An elaborate morphometric evaluation was in keeping with a left-shifting showing a more frequent occurrence of promegakaryoblasts and microforms in both therapy groups. However, contrasting ANA, HU generated defects of differentiation consistent with significant dysplastic changes. In conclusion, concern about a possible leukemogenic capacity following long-term HU therapy is supported by our findings.