Focal cortical dysplasia coexisting with diffuse astrocytoma in childhood: a case report and reappraisal of the glial component in archival FCD cases.

We report a rare case of focal cortical dysplasia (FCD) concurring with diffuse astrocytoma and arachnoid cyst, and also re-evaluate the glial component in archival FCD cases for the differential diagnosis of diffuse gliomas. A 7-year-old boy with a 9-month history of psychomotor seizures disclosed a hyperintense area accompanied by a cystic lesion in the left temporal lobe on MRI. The surgical specimen displayed dyslamination of the cortices and ectopic neurons in the white matter, associated with dysmorphic neurons, indicating FCD type IIA. Additionally, the lesion showed diffuse proliferation and infiltration of glial cells, immunopositive for infiltrating glioma markers (nestin, doublecortin, MAP-2e) and p53, and MIB-1 index was 2.0%. These findings indicated coexisting diffuse astrocytoma. Coexistence of diffuse glioma with FCD is unusual, but we often notice increased population of small glial cells in FCD lesions. Re-evaluation of archival FCD cases with diverse markers revealed that reactive microglia significantly proliferate in the white matter lesions. Therefore, a careful pathological assessment has to be made to define a rare case of diffuse glioma occurring in FCD.