Ectopic choroid plexus found in fetal sections: a case report with literature consideration.

We incidentally found an ectopic choroid plexus (CP) attached to the posterior side of the cervicothoracic spinal cord (C4-T6) in a 16-week aborted fetus. The cytoarchitecture of the cord and segmental nerves showed normal development. The fourth ventricle did not contain the usual CP but a red blood cell cluster due to hemorrhage, although the cause, whether spontaneous or traumatic, was unknown. The ectopic CP was associated with thick neuroepithelium that was strongly positive for glial fibrillary acidic protein, vimentin, nestin, and proliferating cell nuclear antigen, but did not contain any CD34-positive vessels. Thus, the ectopic neuroepithelium seemed not to carry growth factor for vascular development. On the inferior side of the ectopic CP, the lower thoracic cord was wavy, folded, and packed in a limited space as a folding fan. Despite the strange gross appearance, however, we found no abnormality in the dorsal root ganglion, the spinal nerve root, or the cytoarchitecture of the lower thoracic cord. Therefore, the abnormality in the lower thoracic cord seemed to be secondarily induced by trophic factor(s) from the ectopic CP and/or the associated neuroepithelium. This may be the first report on an ectopic CP associated with ectopic neuroepithelium.