Mitotic activity of multinucleated giant cells with glial fibrillary acidic protein immunoreactivity in glioblastomas: an immunohistochemical double labeling study.

To investigate the mitotic activity of multinucleated giant cells (MNGCs) with glial fibrillary acidic protein (GFAP) in glioblastomas, double immunohistochemical staining for GFAP and Ki67 was performed in formalin-fixed and paraffin-embedded specimens obtained from 12 primary glioblastomas with MNGCs including three giant cell glioblastomas. The Ki67 labeling index (LI:%) of GFAP+ tumor cells ranged from 0 to 5.6 (2.5+/-1.7, mean+/-standard deviation). The Ki67 LI of GFAP- tumor cells ranged from 18.6 to 35.9 (24.7+/-6.6). The Ki67 LI of GFAP+ cells was significantly lower than that of GFAP- cells (P<0.0001). The number of Ki67+ GFAP- MNGCs ranged from 0 to 23 (8.6+/-8.2). The number of Ki67- GFAP+ MNGCs ranged from 0 to 15 (6.2+/-5.1). There was no significant difference between them (P=0.42). The Ki67 LI of GFAP+ MNGCs was 10.4+/-12.6. The Ki67 LI of GFAP- MNGCs was 45.9+/-29.9. The Ki67 LI of GFAP+ MNGCs was significantly lower than that of GFAP- MNGCs (P<0.01). Our study suggested that MNGCs with mitotic capacity were not dominant and that GFAP+ MNGCs had little mitotic activity in glioblastomas. MNGCs identified in glioblastomas may develop via not only the proliferation of abnormal nuclei in a single tumor cell but also other processes.