ABSTRACT
Immature teratoma of the human ovary is a rare disease, and its diagnosis and grading are currently based on histologic evaluation of the presence and amount of immature neural components in the tumor. Despite the importance of tumor grading, immature neural components especially without rosette formation are difficult to identify, partly because useful biomarkers for them are not yet available. Toward this goal, we investigated 16 immature teratomas from human ovaries as well as 10 of those derived from murine embryonic stem cells transplanted into immunodeficient mice. Immunohistochemistry was performed for cytokeratin, glial fibrillary acidic protein, S100, and fascin. It was demonstrated that glial fibrillary acidic protein and S100 expression was not observed in the immature neural components of immature teratomas derived from both human ovary and embryonic stem cells, although their expression was detected in mature neural tissues. In contrast, fascin immunopositivity was clearly found in both mature and immature neural components regardless of rosette formation in immature teratomas derived from both human ovary and embryonic stem cells. Assessment of immature neural components by fascin immunostaining yielded the same or slightly increased quantity than quantification based on hematoxylin and eosin staining. These results suggest that fascin immunostaining is useful as a biomarker in correctly diagnosing and grading human immature teratomas. Further, fascin immunostaining may contribute to the development of regenerative medicine through accurate assessment of the maturation status of pluripotent stem cell-derived tumors transplanted into immunodeficient mice.