[Analysis of the proliferative potential of meningiomas with MIB-1 monoclonal antibodies]

Tumor recurrence was observed in 12 (11.3%) out of 106 cases of intracranial meningioma followed for more than 5 years. Proliferative potential was evaluated immunohistochemically with MIB-1 monoclonal antibodies in 37 cases of non-recurrent meningioma and 12 cases (21 samples) of recurrent meningioma. The proliferating cell index (PCI) was much higher in the non-recurrent meningiomas than the recurrent meningiomas (10.6 +/- 7.7 [mean +/- SD] versus 1.9 +/- 1.5). Most recurrent meningiomas had high PCI values, greater than 3%. High PCI values of more than 5% were found in 13 (62%) of the 21 samples of recurrent meningioma. However, only 4 of the 37 cases of nonrecurrent meningioma had high PCI values with MIB-1 of more than 3%. The 12 cases of recurrent meningioma were classified into 3 groups: 6 cases in which both the initial and recurrent meningiomas were benign (Group I), 5 cases in which the meningioma at the time of the initial operation was benign, but the recurrent meningioma was malignant (Group II), and one case in which malignant meningioma was diagnosed at the time of the initial operation (Group III). The PCI values with MIB-1 in most of the recurrent meningiomas were higher at the time of recurrence than at the time of the initial operation. Malignant meningiomas, such as anaplastic and atypical meningioma, and some meningotheliomatous meningiomas among the benign meningiomas recurred and had higher PCI with MIB-1 values than other meningiomas. It is concluded that PCI with MIB-1 is important as a predictive factor for the recurrence of meningiomas. Meningiomas having a PCI value with MIB-1 of more than 3% in particular should be followed carefully.