Poster Presentation ESA-SRB 2023 in conjunction with ENSA

Clinical behaviour of multilineage tumours expressing PIT1 and SF1 in a cohort of tumours at Westmead Hospital (#251)

Prishila Fookeerah 1 2 , Winny Varikatt 3 4 , Meena Shingde 3 4 , Mark AJ Dexter 4 5 , Mark Mclean 1 2
  1. Department of Diabetes and Endocrinology, Westmead Hospital, Sydney, NSW, Australia
  2. School of Medicine, Western Sydney University, Sydney, NSW, Australia
  3. Department of Tissue Pathology and Diagnostic Oncology, Westmead Hospital, Sydney, NSW, Australia
  4. Westmead Clinical School, University of Sydney, Sydney, NSW, Australia
  5. Department of Neurosurgery, Westmead Hospital, Sydney, New South Wales, Australia

Background

Multilineage PIT1 and SF1 pituitary neuroendocrine tumours (PitNETs) are a rare morphological subtype consisting of a single tumour population co-expressing transcription factors PIT1 and SF1. These tumours may also demonstrate variable combinations of hormonal immunostaining corresponding to both lineages. Clinical manifestations can vary depending on the dominant hormone secreted by the tumour. The overall clinical behaviour and prognosis of these PitNETs is not known.

Methods

We performed a retrospective assessment of the histological characteristics and clinical outcomes of a series of nine multilineage PIT1 and SF1 PitNETs identified from a cohort of 246 pituitary tumours at Westmead Hospital. Tumours were assessed for the presence of pituitary transcription factors, hormonal expression and somatostatin receptor (SSTR) status using immunohistochemistry. Clinical data for each tumour was reviewed.

Results

These tumours represented 3.7% of our PitNET cohort. Eight tumours (88.9%) expressed growth hormone and caused acromegaly at presentation. One tumour did not express any PIT1 lineage hormones. Of the 7 macrotumours that caused acromegaly, only one had radiological cavernous sinus invasion. Ki 67 labelling index was low, ranged from 0.6 to 3.6%. 88% of tumours secreting excess growth hormone exhibited strong immunostaining for SSTR2 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 all 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 (12-132 months).

Conclusion

The majority of multilineage PIT1 and SF1 tumours were macrotumours expressing growth hormone and causing acromegaly. Surgical cure was achieved in over 60% of tumours causing acromegaly. Overall prognosis appears favourable over a mean follow up of approximately 5 years.