Classic chordoma coexisting with benign notochordal cell rest demonstrating different immunohistological expression patterns of brachyury and galectin-3

Increasing numbers of studies support the hypothesis that chordoma arises from notochordal cell rests, although the mechanism awaits further research. Brachyury is the first specific molecule linking chordoma with the notochord, and galectin-3 has been widely used as a marker of notochordal cells. We conducted a histological study of the expression of these two molecules in 46 classic chordoma specimens and unexpectedly found that classic chordoma tumor cells coexisted with benign notochordal cell rests in six specimens. Brachyury and galectin-3 expression were investigated by immunohistochemistry. All specimens contained atypical chordoma tumor cells set within an abundant myxoid matrix, which strongly expressed brachyury and galectin-3. However, brachyury and galectin-3 were not expressed in the notochordal cells. Benign notochordal cells, present as notochord rests, could undergo malignant transformation to form chordoma; however, the cause and role of brachyury and galectin-3 expression in chordoma tumorigenesis requires further careful study.