Objective: Posterior pituitary tumours (PPTs) are rare neoplasms with the four recognised subtypes unified by thyroid transcription factor-1 (TTF-1) expression, according to the 2017 WHO classification. Though traditionally defined as low grade neoplasms, a substantial proportion of them show recurrence/persistence following surgery.
Methods: We selected patients with PPTs in our cohort of 1760 patients operated for pituitary tumours over the past ten years. The clinical, radiological, hormonal, histopathological profiles and long-term outcomes of the three cases identified (two pituicytomas and one spindle cell oncocytoma, SCO) were analysed. Following a literature review, data of all published cases with documented TTF-1 positive pituicytomas and SCOs were analysed to determine the predictors of recurrence/persistence in these tumours.
Results: Patients presented with compressive features or hypogonadism. Two had sellar-suprasellar masses. One had a purely suprasellar mass with a pre-operative radiological suspicion of pituicytoma. Two were operated by transsphenoidal surgery and one transcranially guided by neuronavigation. Histopathology confirmed spindle cells in a storiform arrangement and low Ki67 index. Immunohistochemistry showed positive TTF-1, S-100 expression and variable positivity for EMA, vimentin and GFAP. Re-evaluation showed recurrence/persistence in two patients. A literature review of recurrent/persistent pituicytoma (n=17) and SCO (n=9) cases revealed clinical clues (headache for pituicytomas, male gender for SCO), baseline tumour size (≥20.5mm with sensitivity exceeding 80%) and longer follow-up duration as determinants of recurrence/persistence.
Conclusion: PPTs are rare sellar masses with quintessential TTF-1 positivity. Recurrent/persistent disease following surgery is determined by greater tumour size at baseline and duration of follow-up. This warrants intensive and long-term surveillance in these patients.