Assessment of ARX expression, a novel biomarker for metastatic risk in pancreatic neuroendocrine tumors, in endoscopic ultrasound fine-needle aspiration.

Wenzel M Hackeng,G Johan A Offerhaus,Koen M A Dreijerink,Folkert H M Morsink,Christopher M Heaphy,Lodewijk A A Brosens,Leon M G Moons

doi:10.1002/dc.24368

Wenzel M Hackeng, G Johan A Offerhaus + Show 5 more

Open Access

https://doi.org/10.1002/dc.24368

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Abstract

BackgroundThe transcription factors ARX and PDX1, and alternative lengthening of telomeres (ALT) were recently described as prognostic markers for resected non‐functional pancreatic neuroendocrine tumors (PanNETs). ALT positive tumors with ARX expression relapse most often. Currently, tumor size is the only preoperative marker used to decide whether or not to operate, thus additional preoperative prognostic markers are needed. Therefore, it is critical to assess the performance of these biomarkers on preoperative cytologic specimens.MethodsEndoscopic fine‐needle aspiration cellblock material and corresponding surgical specimens of 13 patients with PanNETs were assessed for histology, immunohistochemical staining of ARX, PDX1, Synaptophysin, Ki67, and telomere‐specific fluorescence in situ hybridization to detect ALT, and then associated with clinicopathological features. Scoring for ARX and PDX1 was performed blinded by two independent observers.ResultsOf the 13 surgical specimens, 8 were ARX+/PDX1−, 2 ARX−/PDX1+, and 3 ARX+/PDX1+. Concordance between cytologic and surgical specimens for ARX protein expression was 100%, whereas concordance for PDX1, ALT, and WHO tumor grade was 85%, 91%, and 73%, respectively. There was a perfect inter‐observer agreement in ARX and PDX1 scoring.ConclusionARX can reliably be determined in cytologic specimens and has low inter‐observer variability. For cytology, false‐positive PDX1 expression was observed, possibly due to contamination or sampling, while ALT had a false‐negative case due to incomplete sampling. As previously observed, tumor grade is underestimated in cytologic specimens. Thus, ARX and ALT are the most promising markers to predict metastatic behavior in PanNETs, thereby warranting further validation in larger studies.

Highlights

Neuroendocrine tumors of the pancreas (PanNET) are the second most common malignancy of the pancreas
This study aims to answer these questions and provide the framework for further optimization of ARX and PDX1 staining in combination with alternative lengthening of telomeres (ALT) as preoperative markers, thereby justifying independent validation of these markers in large, prospective trials
ARX expression was found to be perfectly concordant between preoperative cytologic specimens and postoperative surgical specimens and there was no inter-observer variation

Summary

| INTRODUCTION

Neuroendocrine tumors of the pancreas (PanNET) are the second most common malignancy of the pancreas. PDX1 or double positive expression on the other hand identified a more indolent group, in which only few tumors relapsed.[12] Chan et al showed, using RNA sequencing and whole genome methylation, that the ARX positive, PDX1 negative subgroup was often associated with somatic mutations in ATRX, DAXX, or MEN1 and a worse prognosis.[13]. ARX and PDX1, in combination with ALT, may be prognostic markers to identify low and high risk subgroups preoperatively on cytology, as staining of these proteins seems to identify these alpha and beta cell-like subgroups robustly. This study aims to answer these questions and provide the framework for further optimization of ARX and PDX1 staining in combination with ALT as preoperative markers, thereby justifying independent validation of these markers in large, prospective trials

| METHODS

| RESULTS

Findings

| DISCUSSION