CORTICAL ARCHITECTURAL ABNORMALITIES AND MIB1 IMMUNOREACTIVITY IN GANGLIOGLIOMAS - A STUDY OF 60 PATIENTS WITH INTRACRANIAL TUMORS

Gangliogliomas are generally low grade neoplasms composed of mixtures of neoplastic glial and neuronal elements whose origin and exact natur e are still controversial. We studied a series of 60 intracranial gang liogliomas looking for coexistent cortical architectural abnormalities (cortical dysplasia, microdys,genesis) and to determine if tumor beha vior correlates with MIB1 (marker of cellular proliferation) labeling. The patients included 34 males and 26 females who ranged in age from 6 months to 55 years (mean 20 years). Thirty-eight tumors (63%) were l ocated in the temporal lobe and 6 (10%) in the frontal robe. Fifty-fou r patients (90%) presented with seizures (most with intractable epilep sy) and the duration of seizures ranged from 1 to 38 years (mean 14 ye ars). In all cases, the predominant glioma component resembled a low g rade fibrillary astrocytoma. In 14 tumors (23%), an oligodendroglial c omponent was present. In one case, the glial component resembled an an aplastic astrocytoma. The tumors were characterized variously by periv ascular chronic inflammation (N = 45, 75%), vascular proliferation (N = 36, 60%), granular bodies (N = 54, 90%), binucleated neurons (N = 36 , 60%), calcification (N = 28, 47%), and cystic degeneration (N = 26, 43%). Meningeal involvement by tumor was observed in five (8%) cases. In 38 patients, sufficient tissue was resected to evaluate for the pre sence of concomitant cortical architectural abnormalities. Cortical ar chitectural abnormalities were identified near to but clearly separate from the tumor in 19 (50%) patients. Only four patients including the anaplastic tumor died with tumor progression. MIB1 indices (positive tumor cells/1,000 tumor cells counted) in 54 cases ranged from 0 to 10 .2 (mean 1.1 +/- 1.0). Mortality did not reliably correlate with the M IB1 index; however the highest index was observed in the anaplastic tu mor. The high incidence of associated architectural abnormalities sugg ests that gangliogliomas may arise on a maldevelopmental basis. Althou gh generally benign and slow-growing tumors, as indicated by the gener ally low MIB1 indices, gangliogliomas can rarely behave in a malignant fashion. It is not possible to reliably predict prognosis on the basi s of histologic features or MIB1 immunoreactivity.