Objectives Ecchordosis physaliphora (EP) is a benign, usually asymptomatic, notochord tumour but may also present with a spontaneous CSF fistula. Differentiating EP from its more aggressive counterpart, chordoma is challenging but important as the clinical course and management differ significantly, with the latter requiring proton beam radiotherapy. This case series aims to further inform this discussion.

Design Case series.

Subjects Patients with suspected EP from 2015–2018.

Methods Retrospective analysis.

Results Six patients were identified. Four presented with suspected CSF leak. MRI revealed a T1-hypointense and T2-hyperintense clival lesion without enhancement. CT showed pneumocephalus, a clival defect and no mass lesion. All underwent endoscopic endonasal repair of CSF fistula with biopsy. Histology revealed physaliphorous cells with no mitoses; immunohistochemistry confirmed notochord origin (EMA, S100, CD10 and/or MNF116) and low proliferation index. In 2 patients, EP was found incidentally on imaging and these lesions have remained static on follow-up.

Conclusions In the absence of a clival mass, notochord remnant lesions with benign histopathology can be treated as EP and patients can avoid radiotherapy. The diagnosis of EP, however, remains challenging as no distinctive histopathological marker exists to differentiate it from chordoma and until a genetic or immunohistochemical marker is identified, the diagnosis rests solely on the presence or absence of a mass on imaging.