title: Diagnosing an extra-axial chordoma of the proximal tibia with the help of brachyury, a molecule required for notochordal differentiation.
abstract: Chordomas are rare malignant bone tumours considered to arise from notochordal remnants that persist in the axial skeleton. Although their morphology can resemble that of a carcinoma, chondrosarcoma or malignant melanoma, the axial location and their well-defined immunophenotype, including expression of cytokeratins (CK7/20/8/18/19) and S100, generally allow the diagnosis to be made with confidence once the possibility is considered. In contrast, making a robust diagnosis of an extra-axial chordoma has been difficult in the absence of specific markers for chordomas. We have recently shown in gene expression microarray and immunohistochemistry studies that brachyury, a transcription factor crucial for notochordal development, is a specific and sensitive maker for chordomas. We now present a case of an intracortical tibial tumour, with detailed report of the imaging, and morphological features consistent with a chordoma, where notochordal differentiation was demonstrated with an antibody to brachyury. The tumour cells were also positive for cytokeratins, including CK19, and S100, CEA, EMA and HMBE1, findings which support the diagnosis of chordoma. Brachyury can be employed as a marker of notochordal differentiation and help identify confidently, for the first time, extra-axial bone and soft tissue chordomas, and tumours which may show focal notochordal differentiation.
authors.affiliation: Department of Radiology, Royal National Orthopaedic Hospital, Stanmore, Middlesex, HA7 4LP, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: O'donnell
authors.forename: Roberto
authors.initials: R
authors.lastname: Tirabosco
authors.forename: Sonja
authors.initials: S
authors.lastname: Vujovic
authors.forename: William
authors.initials: W
authors.lastname: Bartlett
authors.forename: Timothy W R
authors.initials: TW
authors.lastname: Briggs
authors.forename: Stephen
authors.initials: S
authors.lastname: Henderson
authors.forename: Chris
authors.initials: C
authors.lastname: Boshoff
authors.forename: Adrienne M
authors.initials: AM
authors.lastname: Flanagan
mesh_terms: D000328:Adult; D001859:Bone Neoplasms / Q000175:diagnosis* / Q000378:metabolism* / Q000601:surgery; D002817:Chordoma / Q000175:diagnosis* / Q000378:metabolism* / Q000601:surgery; D005326:Fetal Proteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D020825:T-Box Domain Proteins / Q000378:metabolism*; D013977:Tibia; D000098908:Brachyury Protein
chemical_list: D005326:Fetal Proteins; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein