S-100 protein immunostaining in teratomatous well-differentiated tissues.

The presence and distribution of S-100 protein were studied in a case of ovarian teratoma using avidin-biotin complex immunoperoxidase method. S-100 immunoreactivity within the well-differentiated teratomatous tissues appeared to mirror that of their normally developed human counterparts, although we could unexpectedly detect S-100 immunoreactivity in bone osteoblasts and osteocytes, and in tooth germ odontoblasts. Choroid plexus-like formations present in the teratoma were also positive. Our results suggest that the presence of S-100 protein might be associated with a basic cell function regardless of the presence of a physiologically end-developed human organism.