Cell differentiation in sacrococcygeal teratomas. An immunohistochemical and follow-up study.

The cell differentiation properties of thirty-four sacrococcygeal teratomas (SCT) and their five recurrences were immunohistochemically studied for the expression of different classes of intermediate filament proteins, muscle actin (MA) and S-100 protein. Out of thirty-nine tumors twenty-three were SCTs with only mature tissue elements, seven immature teratomas, five pure endodermal sinus tumors (EST) and four ESTs or embryonal carcinomas (EC) combined with mature components. Cytokeratin positivity was found in all epithelial structures and sometimes also in smooth muscle and primitive mesenchymal cells. An intense cytokeratin immunoreactivity was observed in EC and EST components. Muscle markers, desmin and MA were present in smooth and striated muscle cells. Focal desmin positivity was also found in some epithelial structures in two cases. Glial tissue positive for glial fibrillary acidic protein (GFAP) was found in twenty-eight out of thirty-nine tumors. Some cases with no apparent glial tissue in hematoxylin and eosin staining showed glial differentiation as proved by GFAP positivity. In six out of eleven choroid plexus-like tissues GFAP positive cells were observed. S-100 protein showed an intense distribution of immunoreactivity outside neural tissue, and focal positivity was observed in malignant epithelial structures. Immunohistochemical markers did not reveal any prognostic significance in teratomas. Our findings, however, showed some aberrant features of cell differentiation from normal mature tissue components but closely parallel to those found in normal fetal development.