HAM56-immunoreactive macrophages in untreated infiltrating gliomas

Context.-Classic diagnostic neuropathologic teachings have cautioned agains t making the diagnosis of neoplasia in the presence of a macrophage populat ion. The knowledge of macrophage distribution should prove useful when conf ronted with an infiltrating glioma containing macrophages. Objective.-To identify macrophages in untreated, infiltrating gliomas using the monoclonal antibody HAM56, and to confirm their presence in an untreat ed glioblastoma multiforme (GBM) with the serial analysis of gene expressio n (SAGE) method. Methods.-We evaluated the presence of macrophages in 16 cases of untreated, supratentorial infiltrating gliomas with the macrophage monoclonal antibod y HAM56. We performed SAGE for one case of GEM and for normal brain tissue. Results.-In World Health Organization (WHO) grade II well-differentiated as trocytoma and oligodendroglioma, HAM56 reactivity was noted only in endothe lial cells, and unequivocal macrophages were not identified. In WHO grade I II anaplastic astrocytoma and anaplastic oligodendroglioma, rare HAM56-posi tive macrophages were noted in solid areas of tumor. In WHO grade IV GBM, H AM56-positive macrophages were identified in areas of solid tumor (mean lab eling index, 8.6%). In all cases of GEM, nonquantitated HAM56-positive macr ophages were identified in foci of pseudopalisading cells abutting necrosis and in foci of microvascular proliferations. In none of the cases were gra nulomas or microglial nodules found, and there was no prior history of surg ical intervention, radiation therapy, chemotherapy, or head trauma in these cases. By SAGE, the macrophage-related proteins osteopontin and macrophage -capping protein were overexpressed 12-fold and eightfold, respectively, in one untreated GBM compared with normal brain tissue. In this case, numerou s HAM56-positive macrophages (labeling index, 24.5%) were present in the so lid portion of tumor, and abundant nonquantified macrophages were identifie d in foci of pseudopalisading cells abutting necrosis and in foci of microv ascular proliferations. Conclusions.-This study confirms the utility of the monoclonal antibody HAM 56 in identifying macrophages within untreated infiltrating gliomas. The ov erexpression of macrophage-related proteins in one case of GEM as detected by SAGE signifies that macrophages may be present in untreated GBMs.