Somatostatin receptor expression and clinical outcome of multilineage pituitary tumours expressing PIT1 and SF1

Prishila Fookeerah; Winny Varikatt; Meena Shingde; Mark A J Dexter; Mark McLean

doi:10.1530/EC-23-0328

Somatostatin receptor expression and clinical outcome of multilineage pituitary tumours expressing PIT1 and SF1

Endocr Connect. 2023 Oct 9;12(11):e230328. doi: 10.1530/EC-23-0328. Print 2023 Nov 1.

Authors

Prishila Fookeerah^{1

2}, Winny Varikatt^{3

4}, Meena Shingde^{3

4}, Mark A J Dexter^{4

5}, Mark McLean^{1

2}

Affiliations

¹ Department of Diabetes and Endocrinology, Westmead Hospital, Sydney, Australia.
² School of Medicine, Western Sydney University, Sydney, Australia.
³ Department of Tissue Pathology and Diagnostic Oncology, Westmead Hospital, Sydney, Australia.
⁴ Westmead Clinical School, University of Sydney, Sydney, Australia.
⁵ Department of Neurosurgery, Westmead Hospital, Sydney, Australia.

Abstract

The application of transcription factor immunohistochemistry to pituitary neuroendocrine tumour (PitNET) assessment has allowed identification of tumours that do not conform to a single lineage. Multilineage pituitary transcription factor 1 (PIT1) and steroidogenic factor 1 (SF1) PitNETs are a rare and relatively newly described tumour subtype. These tumours express both transcription factors and may also express combinations of hormones corresponding to both lineages. Histological and clinical characteristics can vary, and overall clinical behaviour and prognosis is not known. We describe the clinical outcomes and somatostatin receptor status (SSTR) of a series of nine cases identified from our cohort of pituitary tumours at Westmead Hospital. Eight PitNETs (88.9%) expressed growth hormone and caused acromegaly at presentation. Of the seven macrotumours that caused acromegaly, one had cavernous sinus invasion. The Ki-67 labeling index score ranged from 0.6% to 3.6%. About 88% of tumours that secreted excess growth hormone exhibited strong immunostaining for SSTR 2 and all tumours displayed weak immunoreactivity for SSTR5. In 62.5% of patients with acromegaly, cure was achieved after surgical resection. Somatostatin receptor ligands resulted in clinical remission in cases where medical treatment was initiated. There was no new tumour recurrence or regrowth over an overall mean follow-up period of 62.5 months.

Keywords: acromegaly; multilineage PIT1 and SF1; pituitary adenomas; pituitary neuroendocrine tumours; plurihormonal; somatostatin receptor; transcription factor.