Benign Notochordal Cell Tumour

Both the benign notochordal cell tumour and chordoma arise from notochordal tissue in the axial skeleton - the clivus, vertebral bodies and sacrum - and both are brachyury-positive, so the distinction rests largely on the imaging assessment of aggressiveness, supported by histology. A benign notochordal cell tumour is typically an incidental, intraosseous lesion that is sclerotic, or mixed sclerotic, on CT with marrow signal change on MRI, and crucially it shows no bone destruction and no extraosseous soft-tissue mass - this contained, non-aggressive, sclerotic appearance is the hallmark of its benign nature. A chordoma, by contrast, is lytic and destructive, with an extraosseous soft-tissue mass and a myxoid, lobulated architecture, and the patient is more likely to be symptomatic. Histologically, the benign tumour is sheets of bland, vacuolated, adipocyte-like notochordal cells filling the marrow without chordoma's myxoid matrix, lobular architecture and destruction, although immunohistochemistry alone does not separate them. The decision matters greatly because the benign notochordal cell tumour, if asymptomatic, is managed by observation with imaging surveillance - partly to confirm stability and exclude evolution to chordoma, of which it may be a precursor - whereas a chordoma requires wide or en-bloc oncological resection with consideration of radiotherapy such as proton therapy. So for this incidental sclerotic lesion with no destruction or soft-tissue mass, I would favour a benign notochordal cell tumour and observe it, while managing any equivocal or aggressive axial notochordal lesion at a specialist spine and tumour centre.