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 vestibular schwannomas in 46 patients with neurofibromatosis 2 (NF2), and 50 patients with unilateral vestibular schwannomas were investigated immunohistochemically with the monoclonal antibody MIB 1 directed against recombinant 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 compared to clinical and histological findings in both groups. There was 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 maximal 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 schwannomas. These differences may express immunohistochemically some clinical and morphological differences between bilateral and unilateral vestibular schwannomas.