Immunohistochemical investigation of chordomas: histogenetic and differential diagnostic aspects

Chordomas are rare tumors of neuroectodermal origin and often show a very heterogeneous histological picture. In a combined histochemical and immunohistochemical study of 32 chordomas collected in the Bone Tumor Registry of Westphalia we were able to show that the immunoreactivity of the cells in both chordoma and notochordal structures are in close relationship with the extracellular matrix and depends more on the metabolic activity of these cells than on the origin of the cells of the neuroectoderm. All tumor cells show a bimodal immunoreaction with cytokeratin and vimentin, as well as a strong immunoreaction with the oncofetal markers CEA and AFP. The differentiation of chordomas from other malignant tumors, mainly the myxoid variant of chondrosarcoma, may cause major difficulties, especially if only a little biopsy material is available. Here we can see that in tumors with bimodal immunoexpression of vimentin and cytokeratin, as can be found in chordomas, the further use of antibodies offers a reliable differential diagnostic tool. The positive reaction of chordomas with all epithelial tumor markers offers a clear differentiation from chondrosarcomas, which, unlike chordomas, do not express cytokeratin. The identification of a marker profile by employing common antisera is of major value in the differentiation of chordoma from other epithelial or mesenchymal tumors.