Immunophenotypic features of immaturity of neural elements in ovarian teratoma.

Neural components in mature teratomas are common and the general assumption is that they are quite similar to those in the mature central nervous system (CNS). We investigated 44 ovarian teratomas by immunohistochemistry to determine cellular and structural immaturity of neural elements. Most teratomas contained cells differentiating into astrocytes positive for nestin, a neural stem cell marker. These nestin-positive astrocytes generally co-expressed glial fibrillary acidic protein-delta, an immature astrocyte marker. Olig2-positive cells were randomly scattered. Areas comprising cells that differentiated into neurons were positive for NeuN and synaptophysin. The border between white and gray matter was ill-defined and more NeuN-positive cells were distributed in areas that were positive for myelin basic protein, indicating that the distribution of neurons and glial cells was disturbed. Peripheral nerve bundles positive for Schwann/2E, an antigen specific for myelinating Schwann cells, were mixed within CNS-like tissues. These results show that apparently mature teratomas are not in fact mature, at least in terms of neural elements, as they harbor immature cells and structural abnormalities. The neural elements of surgically resected teratomas might represent a premature state of the human CNS, and thus be potentially useful for studies of developmental neurobiology as well as gliomagenesis.