Tissue polypeptide antigen staining of the chordoma and notochordal remnants.

Tissue polypeptide antigen (TPA) has been increasingly used as an immunological marker for tumors derived from the lining epithelia of body cavities, including those of the gastrointestinal tract and genitourinary and bronchopulmonary systems. Here, we present evidence that this antigen is consistently and strongly expressed by a nonepithelial lesion - the chordoma. Irrespective of their sites, all seven chordomas, including one chondroid lesion, were heavily stained. In contrast, five chondrosarcomas were unstained or showed only focal slight positivity. TPA staining was also found to be strongly expressed by notochordal rests within the intervertebral disks of one newborn and five fetuses (15th to 32nd week of gestation), adding further evidence that these rests are the histogenetic origin of the chordoma.