The sections include cerebral cortex and white matter. The neurones in the cortex are focally disorganised and show crowding. The lamination pattern of the cortical layers is distorted. The cytoplasmic processes run in different directions. The neurones show nuclear enlargement with prominent nucleoli. Some bi or multinucleated forms are seen. The Nissl substance in the cytoplasm shows clumping. There are scattered balloon cells with abundant eosinophilic cytoplasm. Increased numbers of neurones are present in the white matter. They do not form a discrete mass. The adjacent astrocytes show reactive gliosis. No evidence of malignancy is identified. IDH-1 immunostain is negative. The topoisomerase index is less than 1%. The features are those of focal cortical dysplasia (ILAE type IIb).
Final diagnosis:
Brain tissue: Focal cortical dysplasia (ILAE type IIb).