Posterior pituitary tumours: patient outcomes and determinants of disease recurrence or persistence

Abstract

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 10 years (2010-2019). 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 (≥20.5 mm 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.

Keywords: TTF-1; pituicytomas; posterior pituitary tumours; spindle cell oncocytomas.

Figure 1

Panel of MRI images of Patient 1 (spindle cell oncocytoma). (A) showing a sellar-suprasellar mass (2.1 × 2 × 1.4 cm) abutting the optic chiasm and partially encasing both cavernous sinuses with preserved flow voids showing uniform enhancement on contrast administration (B). Sagittal MRI images without (C) and with (D) contrast show the sellar mass with a suprasellar extension. The pituitary and stalk are not separately visible. Bottom panel (E, F, G and H) shows post-operative MRI images of patient 1 with (E) showing post-operative changes (red arrow) and subsequent yearly images (F, G and H) showing a right-sided intrasellar recurrence (0.8 × 0.7 × 1.0 cm) which has remained stable over the past 3 years (green arrows).

Figure 2

MRI of Patient 3 (pituicytoma) with the top panel showing a homogeneously enhancing well-defined mass (1.7 × 1.6 × 1.8 cm) on axial sections (A) in the sellar region and (B) showing a pure suprasellar mass (yellow arrow) with the pituitary seen separately from the lesion. The mass reaches the floor of the third ventricle and bilateral cavernous flow voids are maintained. Bottom panel ((C) without contrast and (D) with contrast, red and green arrows) showing sagittal sections of the same suprasellar mass in which the mass seems to be abutting/arising from the stalk while the pituitary is clearly separate from the lesion. (E and F) show the post-operative MRI of the patient with no tumour residue (white arrow).

Figure 3

Photomicrographs (A and B) show tumour cells arranged in organoid pattern and small groups separated by fine fibrovascular septae. Individual tumour cells are oval to spindle-shaped with pale oeosinophilic moderate-to-abundant fibrillary cytoplasm (H&E staining, ×400). (C) shows nuclear positivity staining (marked by arrows) for immunohistochemistry for thyroid transcription factor 1 (TTF-1) (peroxidase anti-peroxidase, ×500, yellow arrows). (D) shows negative immunohistochemistry staining for epithelial membrane antigen.