MEDIASTINAL GRANULOCYTIC SARCOMA - A REPORT OF 2 CASES

We describe the cases of two patients who presented with granulocytic sarcoma with mediastinal involvement 15 and 21 months before developme nt of acute myeloid leukemia. In both cases several bone marrow aspira tes and trephine biopsy specimens, obtained at presentation and subseq uently, revealed no evidence of leukemic infiltration. One case was or iginally misdiagnosed as large-cell non-Hodgkin's lymphoma, which resu lted in inappropriate therapy. In both cases immunohistochemical stain ing revealed that tumor cells were positive for leucocyte common antig en but not for conventional B- or T-lymphoid-cell markers. Retrospecti ve analysis revealed that tumor cells in both cases were positive for myeloid markers. Histopathologists should be aware that granulocytic s arcoma may occur in unusual extramedullary sites without evidence of b one marrow involvement. If inappropriate treatment is to be avoided, a diagnosis of granulocytic sarcoma should be considered when hemopoiet ic tumor cells do not stain with conventional antibodies against B-and T-lymphoid cells. Both histochemical and immunohistochemical staining should be performed in such cases to determine whether the cells are of myeloid lineage. A diagnosis of granulocytic sarcoma is not ruled o ut when bone marrow biopsy specimens show no evidence of leukemic infi ltration.