Granulocytic sarcoma of megakaryoblastic differentiation in the lymph nodes terminating as acute megakaryoblastic leukemia in a case of chronic idiopathic myelofibrosis persisting for 16 years

A 43-yr-old Japanese woman presented with mild anemia, leukocytosis and spl enomegaly in May 1984. Splenomegaly and anemia gradually progressed. Sixtee n years later, in October 2000, she developed inguinal lymphadenopathy. Bio psy of the lymph node revealed infiltration of blasts, megakaryocytes, fibr oblasts and myeloid cells. Large blasts with basophilic cytoplasm with cyto plasmic projections appeared in the peripheral blood. These blasts were neg ative in peroxidase stain, positive in acid phosphatase and weakly positive in periodic acid-Schiff stain. Immunohistochemical staining with monoclona l antibodies revealed that these blasts were positive with anti-CD41 (glyco protein IIb/IIIa) and negative with other monoclonal antibodies. So diagnos is of granulocytic sarcoma in megakaryoblast ic transformation from chronic idiopathic myelofibrosis was made. A cytogenetic study revealed that bone marrow cells were 46,XX del(13)(q?) initially and additional abnormalities including der(5,5,11)(q11;q13)ins(5;?)(q11;?) were found when she developed megakaryoblastic transformation. Granulocytic sarcoma of megakaryoblastic transformation from chronic idiopathic myelofibrosis is a rare event. Immun ophenotyping with monoclonal antibody for CD41(glycoprotein IIb/IIIa) confi rmed the diagnosis.