Expression of intermediate filaments in chordomas. An immunocytochemical study of five cases.

An immunocytochemical investigation has been carried out on five cases of chordoma (2 of the sacrum, 2 in the spheno-occipital bone and 1 in the parapharyngeal area) to study the expression of the 5 classes of intermediate filaments (IF): cytokeratin (CK), desmin (DES), GFAP, neurofilaments (NF) and vimentin (VIM). Our results show that constant coexpression of CK, NF and VIM does occur in chordomas, whereas DES and GFAP are not demonstrable in tumor cells. The three detected IF are invariably present in all cell types but not in intracellular vacuoles or in the extracellular mucoid substance. The pattern of immunoreactivity of chordomas appears very unique as very few other neoplasms demonstrate the simultaneous occurrence of 3 distinct IF. Only choroid plexus tumors have been shown to manifest CK-NF-VIM immunoreactivity. The complex immunophenotype of chordomas may be related to their supposed origin from the notochord which normally undergoes conspicuous changes in location and morphology during embryonal development. Such changes might require the contemporary presence of multiple IF; IF expression, in fact, is known to be related to cell function and morphology. Notochordal cells and their neoplastic counterpart may consequently express an IF pattern which reflects unique architectural and morphological variations occurring during embryonal and tumor growth. Together with the speculative value of the detection of CK, NF and VIM in chordomas, the unusual immunocytochemical pattern of these tumors might provide useful diagnostic tool in differential diagnosis.