Endoscopic ultrasonography as a comprehensive tool in the evaluation of pancreatic lesions

Abstract

This article expands upon of endoscopic ultrasound’s (EUS) role in the evaluation of pancreatic lesions, building on findings presented by Ayesha et al and Tasneem et al regarding neuroendocrine tumors. We emphasize the diagnostic and therapeutic utility of EUS not only in solid pancreatic tumors but also in the increasingly prevalent cystic lesions, highlighting its particular relevance in resource-limited settings. By integrating high-resolution imaging, tissue acquisition, biomarker analysis, and minimally invasive interventions into a single platform, EUS addresses key diagnostic and therapeutic challenges, reducing the need for multiple costly procedures and enabling effective management even when access to advanced technologies is limited.

Key Words: Endosonography; Pancreatic cyst; Pancreatic neoplasms; Endoscopic ultrasound-guided fine needle aspiration; Neuroendocrine tumors

Core Tip: Endoscopic ultrasound (EUS) is a minimally invasive, high-resolution modality with growing relevance in the diagnosis and management of pancreatic diseases. In solid tumors like neuroendocrine tumors, EUS combined with fine-needle biopsy enables accurate histological characterization and prognostic stratification. In cystic lesions, EUS-guided fluid analysis using accessible biomarkers such as carcinoembryonic antigen and glucose allows for clinically meaningful subclassification. Additionally, EUS provides therapeutic options including drainage of fluid collections, celiac plexus neurolysis, and tumor ablation. This integrated versatility makes EUS particularly valuable in resource-constrained healthcare settings.

TO THE EDITOR

We read with great interest the recently published articles by Ayesha et al[1] and Tasneem et al[2], which explore endoscopic ultrasound’s (EUS) role in the evaluation of pancreatic neuroendocrine tumors (NETs). These contributions highlight the high diagnostic accuracy of EUS-reportedly up to 100% in the study by Ayesha et al[1]-particularly when combined with fine-needle biopsy (FNB) and immunohistochemical markers such as Ki-67 and synaptophysin[1,2]. Although both studies are limited by their retrospective design and single-center scope, they contribute valuable evidence to the field.

EXPANDING THE ROLE OF EUS IN PANCREATIC LESIONS

While the referenced studies underscore the relevance of EUS in solid tumors such as NETs, its role is equally pivotal in the evaluation of pancreatic cystic lesions, entities that are increasingly detected incidentally and often considered in the differential diagnosis, including cystic variants of NETs[3]. The global rise in the incidence of pancreatic cysts has prompted refinement in risk-based evaluation strategies[4]. These lesions are broadly categorized as mucinous or non-mucinous, based on their ability to produce mucin. According to multiple international and national guidelines, including the Chilean Consensus on Pancreatic Cystic Neoplasms, EUS is primarily indicated for cysts with worrisome or high-risk features[3]. Analysis of cyst contents helps to further subclassify them and identify features that may indicate malignancy and influence management decisions[3,4].

EUS has demonstrated diagnostic accuracies of approximately 76% for serous cystic neoplasms and 84%-86% for mucinous neoplasms[5]. It performs comparably, or even superiorly, to cross-sectional imaging modalities such as magnetic resonance imaging or computed tomography, particularly in identifying multifocal or metachronous lesions[6]. When combined with fine-needle aspiration or FNB, EUS allows for targeted fluid analysis. Cyst fluid analysis enables differentiation between mucinous and non-mucinous lesions using accessible biomarkers such as carcinoembryonic antigen (CEA), glucose, and amylase. A CEA level > 192 ng/mL or glucose < 50 mg/dL is highly suggestive of mucinous cysts, with a diagnostic accuracy of up to 94%[7]. Additionally, the string sign can support these findings, while elevated amylase suggests ductal communication (commonly seen in pseudocysts or mucinous lesions)[5]. Importantly, these low-cost biomarkers serve as effective first-line tools, particularly relevant in resource-limited settings, where more advanced molecular diagnostics may be unavailable.

In solid tumors like NETs, EUS-FNB allows acquisition of tissue samples for immunohistochemistry, enabling the detection of chromogranin A, synaptophysin, and Ki-67. As demonstrated in the studies by Ayesha et al[1] and Tasneem et al[2], this approach facilitates accurate tumor grading and prognostic assessment, even in healthcare environments with constrained resources[1,2]. Similarly, in cystic lesions, EUS-FNB yields cytological material with high specificity (up to 96%) for mucinous cysts, though sensitivity remains modest[8].

Molecular analysis of cyst fluid is an emerging adjunct, particularly useful when obtained fluid volumes are limited (< 1 mL)[9,10]. Detection of KRAS and GNAS mutations provides high specificity for mucinous cysts[10]. However, its overall diagnostic yield remains lower than that achieved through a combination of cytological and biochemical analyses[9]. Moreover, the high cost and limited accessibility of molecular testing restrict its routine implementation, especially in low- and middle-income settings[10]. Notably, some studies have reported no significant diagnostic advantage when KRAS and GNAS testing is added to CEA levels and cytology, suggesting comparable performance between approaches[11,12] and further limiting its clinical utility[10]. As a result, current evidence continues to support the use of traditional widely available biomarkers, such as CEA and glucose, alongside cytological evaluation as first-line approaches in most clinical contexts[12-14].

Beyond diagnostics, EUS has also evolved into a therapeutic platform. EUS-guided interventions include celiac plexus neurolysis for pain control in pancreatic cancer, drainage of pancreatic and peripancreatic fluid collections such as pseudocysts and walled-off necrosis (commonly following pancreatitis), and tumor ablation techniques, which include ethanol lavage in cystic tumors and radiofrequency ablation in selected solid neoplasms[7,15]. These therapeutic applications offer effective alternatives to surgical intervention, with lower complication rates and faster recovery, an especially important consideration for high-risk or surgically unfit patients[15].

Based on our clinical experience, particularly within resource-limited healthcare environments, EUS has demonstrated immense value as both a diagnostic and therapeutic tool. Its real-time imaging capabilities, integration with tissue and fluid sampling, and minimally invasive therapeutic applications provide a compact yet powerful platform, streamlining patient care and reducing reliance on more costly, fragmented diagnostic pathways.

CONCLUSION

EUS now stands as a cornerstone in the comprehensive evaluation and management of pancreatic lesions. Its ability to provide accurate diagnosis, guide prognostication, and deliver minimally invasive therapy within a single platform makes it an indispensable and highly efficient tool, especially where healthcare resources are constrained. The recent contributions by Ayesha et al[1] and Tasneem et al[2] reinforce this utility in NETs and prompt broader recognition of EUS as a central modality in the diagnosis and treatment of pancreatic diseases.