Lightning Talk + Poster ESA-SRB-NZSE-CaSR 2026 in conjunction with ENSA

Validation study of a cost-effective diagnostic algorithm utilising screening transcription factor immunohistochemistry in pituitary tumour characterisation. (143375)

Stephanie Baddock 1 2 , Kyle Lloyd 3 , Julia Low 3 , Peter Earls 3 , Ann I McCormack 1 2 4 , Nele F Lenders 1 2
  1. Department of Diabetes and Endocrinology, St Vincent's Hospital Sydney, Darlinghurst, NSW, Australia
  2. School of Clinical Medicine, St Vincent's Healthcare Clinical Campus, Faculty of Medicine and Health, UNSW, Sydney, NSW, Australia
  3. Department of Anatomical Pathology and Cytopathology, St Vincent’s Pathology, Sydney, NSW, Australia
  4. St Vincent's Centre of Applied Medical Research, St Vincent's Hospital, Sydney, NSW, Australia

This study aimed to validate a previously developed tiered diagnostic algorithm for cost-effective, accurate evaluation of pituitary tumour type using the 2022 WHO Classification of pituitary neuroendocrine tumours (PitNETs).

Retrospective evaluation of prospectively collected transcription factor and anterior pituitary hormone immunohistochemistry (IHC) in PitNETs operated at St Vincent’s Hospitals between 2021 and 2025. Transcription factors included steroidogenic factor 1 (SF1), T-box transcription factor 10 (TPIT) and pituitary specific positive transcription factor (PIT1). Three previously published tiered diagnostic algorithms(1), where hormone IHC was performed selectively based on transcription factor results, were applied to a prospective independent cohort. Diagnostic concordance and cost were compared with the reference standard of comprehensive transcription factor and hormone IHC. 

129 tumours were analysed. When compared to the reference standard, complete concordance for classification of tumour type was achieved with all three algorithms. Each algorithm conferred a cost benefit through reduction in immunostains required. Algorithm 3 resulted in the greatest cost benefit ($274 AUD versus $560 AUD), where hormone IHC was only performed for growth hormone, prolactin and thyroid stimulating hormone in the context of PIT1 positivity. Positive IHC for either TPIT or SF1 required no further immunostains. Findings were consistent with the initial study(1). There were 9 tumours with no distinct cell lineage (8 with dual PIT1 and SF1 positivity; 1 with negative transcription factors). Multiple synchronous tumours occurred in two individuals: one had gonadotroph and corticotroph tumours, and the other had gonadotroph and mature plurihormonal PIT1 lineage tumours.

In this independent validation cohort, selective hormone IHC testing guided by transcription factor positivity accurately and cost-effectively classified PitNETs while still identifying tumours lacking a distinct cell lineage. The reproducibility of these findings supports implementation of this streamlined diagnostic algorithm in clinical practice. The cost reduction may facilitate resource reallocation toward improving understanding of difficult-to-classify PitNETs.

  1. Lenders NF, Chui J, Low J, Inder WJ, Earls PE, McCormack AI. Development of a cost-effective diagnostic algorithm incorporating transcription factor immunohistochemistry in the evaluation of pituitary tumours. Pituitary. 2022 Dec;25(6):997-1003. doi: 10.1007/s11102-022-01284-2. Epub 2022 Oct 22. PMID: 36271964; PMCID: PMC9675696.