Immunohistochemical analysis of developmental neural antigen expression in the balloon cells of focal cortical dysplasia

Balloon cells (BC) are the histological hallmarks of focal cortical dysplasia (FCD). Expression of the neural stem cell surface marker CD133 and other developmental markers was studied in the BC of FCD using formalin-fixed paraffin-embedded tissue from nine patients with FCD. Labeling indexes were calculated for all antibodies. BC were easily identified at the gray–white matter junction and they extended into the white matter. Immunoreactivity in BC was found for the following antigens in nine patients: CD133 (six patients; 22.2 ± 7.7%), CD34 (two patients; 0.4 ± 0.3%), nestin (nine patients; 37.6 ± 8.5%), vimentin (eight patients; 59.2 ± 8.7%), glial fibrillary acid protein (six patients; 34.3 ± 10.4%), microtubule-associated protein 2 (four patients; 8.3 ± 5.0%), neurofilament-middle/high (five patients; 10.2 ± 4.6%) and synaptophysin (three patients; 4.2 ± 3.3%). Neuronal nuclei (NeuN, neuron specific nuclear protein) was not expressed in BC of any patient. The results of this study suggest that BC in patients with FCD originate from glioneuronal precursor cells and that developmental defects of neuronal and glial specifications are important in the histogenesis of FCD.