Endoscopic ultrasound-guided needle-based confocal laser endomicroscopy in solid pancreatic masses

Background and study aims: The differential diagnosis of solid pancreatic masses by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is currently suboptimal in centers that are not equipped with rapid on-site evaluation. Needle-based confocal laser endomicroscopy (nCLE) enables real-time in vivo microscopic imaging during endoscopy. This study aimed to describe nCLE interpretation criteria for the characterization of pancreatic masses, with histopathological correlation, and to perform the first validation of these criteria.

Patients and methods: A total of 40 patients were evaluated by EUS-FNA combined with nCLE for the diagnosis of pancreatic masses. Final diagnosis was based on EUS-FNA histology and follow-up at 1 year. Five unblinded examiners defined nCLE criteria for adenocarcinoma, chronic pancreatitis, and neuroendocrine tumor (NET) using a set of video sequences from 14 patients with confirmed pathology (Step 1). These criteria were retrospectively validated by four independent, blinded examiners using sequences from 32 patients (Step 2).

Results: nCLE criteria were described for adenocarcinoma (dark cell aggregates, irregular vessels with leakages of fluorescein), chronic pancreatitis (residual regular glandular pancreatic structures), and NET (black cell aggregates surrounded by vessels and fibrotic areas). These criteria correlated with the histological features of the corresponding lesions. In the validation review, a conclusive nCLE result was obtained in 75 % of cases (96 % correct). Statistical evaluation provided promising results, with high specificity, and negative and positive predictive values for all types of pancreatic masses.

Conclusion: Considering the low negative predictive value of EUS-FNA, nCLE could help to rule out malignancy after a previous inconclusive EUS-FNA. Larger studies are required to confirm these findings and to establish the role of nCLE in the diagnosis of pancreatic masses.

Trial registration: ClinicalTrials.gov (NCT01563133).

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