Putting a Fine Edge on the Diagnosis of Pancreatic Cystic Lesions: How EUS-FNB Is Reshaping Their Management

Pancreatic cystic lesions (PCLs) are now detected with increasing frequency owing to the widespread, routine use of high-resolution abdominal cross-sectional imaging, especially CT and MRI/MRCP. These cysts are classified as branch-duct intraductal papillary mucinous neoplasms (IPMNs), mucinous cystic neoplasms (MCNs), serous cystic neoplasms (SCNs), cystic neuroendocrine tumors (NETs), and solid pseudopapillary neoplasms (SPNs). Because IPMNs with high-grade dysplasia or adenocarcinoma (HGD/Ca), NETs, and SPNs carry substantial malignant potential, accurate risk stratification is essential for choosing between the discordant interventions of surgery, surveillance, or no follow-up.

MRCP—requiring no contrast injection and entailing no radiation exposure—excels at showing duct–cyst communication, cyst multiplicity, and mural nodules [1]. Endoscopic ultrasound (EUS) further refines characterization when CT/MRI findings are equivocal [2]. Nevertheless, morphology alone rarely suffices to distinguish benign from malignant pathology, and misclassification can expose patients to unnecessary surgery with attendant physical, psychological, and economic costs. Alarmingly, retrospective data reveal that roughly one-third of patients resected for incidental PCLs were misdiagnosed pre-operatively [3, 4]. Although guidelines endorse EUS-guided fine-needle aspiration (FNA) with cytology as the diagnostic “gold standard” [5], pooled sensitivities of 27%–55% [6, 7] severely limit its reliability.

To improve histologic yield, a new generation of EUS fine-needle biopsy (FNB) devices was engineered with fork-tip, Franseen, or other end-cutting geometries capable of retrieving core tissue. Despite these advances, systematic data on their performance characteristics in diagnosing PCLs—diagnostic yield, accuracy, safety, and clinical impact—have remained sparse.

In a recent issue of Digestive Diseases and Sciences, Mishra et al. from the University of Michigan report a single-center study of 100 consecutive patients with PCLs in which EUS-FNB achieved a definitive histologic diagnosis in 60% of cases and, importantly, was linked to more appropriate clinical decisions: Surveillance was terminated for benign cysts, whereas malignant lesions underwent timely resection [8]. The sensitivity for malignancy (72.7%) and the 4% rate of post-procedural pancreatitis illustrate the clinical trade-off between improved diagnosis and procedure-related risk. A notable strength of the study is its emphasis on real-world management outcomes rather than purely technical metrics. Significantly, the authors show that “diagnostic yield” extends beyond mucinous vs. non-mucinous categorization to encompass precise subtyping and dysplasia grading—information that directly alters care pathways.

As with any retrospective, single-center series, selection bias is unavoidable; small or low-risk cysts may have been under-sampled. Only 21 patients proceeded to surgical resection—the definitive benchmark—limiting accuracy estimates. Moreover, some patients and providers continued surveillance despite benign histology, underscoring the complexities of risk perception and shared decision-making. More detailed education about the definitive nature of core biopsies could help avoid unnecessary follow-up. A false-negative case—initially labeled a pseudocyst but ultimately an MCN—highlights the clinical stakes. Misclassification can delay curative surgery; efforts must focus on refining sampling technique, pass number, and target selection to minimize such errors. Needle-tract seeding remains a theoretical but unquantified hazard of cyst puncture; long-term surveillance of patients undergoing EUS-FNB is required to clarify this risk.

Looking ahead, prospective multicenter trials are needed to validate diagnostic accuracy, define pancreatitis risk, and establish standardized FNB protocols. Risk stratification models that integrate FNB histology with guideline criteria could better identify the truly low-risk cysts suitable for discharge. Long-term outcome studies—tracking disease-free survival after resection and stability under surveillance—are essential to understand how histology influences prognosis and healthcare costs. Technique optimization (e.g., ideal needle gauge, ≥ 2 passes, prophylactic strategies) should aim to preserve diagnostic gains while reducing adverse events.

EUS-FNB represents a pivotal advance in the management of pancreatic cystic lesions, supplying histologic certainty that frequently realigns treatment decisions. Although its diagnostic yield is not absolute and pancreatitis risk is non-negligible, careful patient selection and standardized technique can maximize benefit. Large-scale prospective studies will determine how best to incorporate FNB into existing algorithms, striking a safe balance between accuracy and risk, and ultimately deliver more individualized, cost-effective care.

Author Contribution

All phases of this invited commentary were carried out by the sole author, Fumitaka Niiya. Dr. Niiya conceived the scope of the manuscript, conducted the literature review, interpreted the data, drafted the initial version, and performed all subsequent revisions and edits. He also approved the final version and accepts full responsibility for the accuracy and integrity of its content.

Data Availability

No datasets were generated or analyzed during the current study.

Declarations

Competing interests

The authors declare no competing interests.