THE COMPARISON BETWEEN THE GROWTH FRACTION OF BILATERAL VESTIBULAR SCHWANNOMAS IN NEUROFIBROMATOSIS-2 (NF2) AND UNILATERAL VESTIBULAR SCHWANNOMAS USING THE MONOCLONAL-ANTIBODY MIB-1

Formalin-fixed paraffin sections of 55 consecutive bilateral vestibula r schwannomas in 46 patients with neurofibromatosis 2 (NF2), and 50 pa tients with unilateral vestibular schwannomas were investigated immuno histochemically with the monoclonal antibody MIB 1 directed against re combinant parts of Ki-67 antigen. The immunohistochemical staining was carried out on dewaxed microwave oven-processed paraffin sections of formalin-fixed tumour tissues. The labelling index (LI) obtained was c ompared to clinical and histological findings in both groups. There wa s no correlation between the LI and age of the patients, tumour size, or histological type of tumour (Antoni A or B). Vestibular schwannomas in NF2 showed higher LI than unilateral vestibular schwannomas: the m aximal LI found per section (LI max) ranged from 0.4 to 17.6% (mean, 2 .7%) in NF2 schwannomas. and from 0 to 9% (mean, 2.2%) in unilateral s chwannomas. These differences may express immunohistochemically some c linical and morphological differences between bilateral and unilateral vestibular schwannomas.