ABSTRACT
<p><b>OBJECTIVE</b>To investigate the diagnosis and differential diagnosis of granulocytic sarcoma (GS).</p><p><b>METHODS</b>The morphological and immunological characteristics of 12 cases of GS were studied. FAB classification was made by peripheral blood, bone marrow picture and bone marrow biopsy assay.</p><p><b>RESULTS</b>All of the 12 cases presented with lymphadenopathy and soft tissue mass. Histologically, the tissue infiltration of GS was composed of blastic cells with round to oval nuclei showing an even, pale chromatin pattern. Some with cleaved or notched nuclei. There were prominent nucleoli and scant cytoplasm in the cells and mitosis was easily found. Immunohistochemically, CD(45) and lysozyme were positive in all of the cases, MPO in 11 (92%), CD(68) in 10 (83%), CD(34) in 5 (42%), and TdT in 2 cases (17%). CD(15) and Mac387 were mainly expressed in mature granulocytes. Examination of bone marrow sections and marrow aspirate smears showed that out of the 11 cases tested 8 were AML-M(2), 2 AML-M(1) and 1 AML-M(0). Only 1 case was nonleukemic, ie. solitary granulocytic sarcoma.</p><p><b>CONCLUSION</b>Granulocytic sarcomas are difficult to identify in routine paraffin-embedded tissue sections and usually misdiagnosed as non-Hodgkin's lymphomas. Immunohistochemistry study with a panel of antibodies in combination with bone marrow and peripheral blood examination are helpful in identification of granulocytic sarcoma.</p>