[Interhemispheric choroidal epithelial cyst associated with partial agenesis of the corpus callosum: case report and review of the literature].

A case of interhemispheric choroidal epithelial cyst is reported. The patient is a 9-month-old female who was transadmitted to our hospital for further examination because of the enlargement of her head. She had no neurological deficits nor symptoms of increased intracranial pressure. CT scanning performed on admission showed multiple cystic lesions in the right frontoparietal interhemispheric space, whose circumference was partially enhanced with contrast medium. Metrizamide CT cisternography demonstrated no communication between the lesions and the ventricular system. The signal intensity of the cysts was higher than that of cerebrospinal fluid on both T1-weighted and T2-weighted MR images. Sagittal T1-weighted images showed partial agenesis of the corpus callosum. The surgical exploration was performed via interhemispheric approach. The cyst wall was found to be white, relatively rich in vascular components, and was removed as much as possible. The examination of the cyst fluid showed total protein levels of 1250 to 3440 mg/dl, and sugar contents of 43 to 99mg/dl. Callosal agenesis was confirmed at operation. The light microscopic examination revealed that the cyst wall was composed of a single layer of columnar or cuboidal epithelium with occasional papillary configuration and thick collagenous connective tissue. The epithelial cells contained PAS-positive granules in the cytoplasm. Electron microscopy showed numerous club-shaped microvilli with no coating materials, continuous basement membrane, tight junction, interdigitation, and multiple fenestrations of endothelium of stromal vessels. On the basis of these findings, the lesion was diagnosed as choroidal epithelial cyst. In the literature, interhemispheric choroidal epithelial cyst associated with partial callosal agenesis, confirmed ultrastructurally, has not, to out knowledge, been reported.