Endoscopic ultrasound-guided needle-based confocal laser endomicroscopy for diagnosis of solid pancreatic lesions (ENES): a pilot study

Background and study aims: Endoscopic ultrasound-guided needle-based confocal laser endomicroscopy (EUS-nCLE) has been shown to aid in the diagnosis of cystic pancreatic lesions. This is a pilot project to study its findings in patients with solid pancreatic lesions (SPLs) with a prospective single-blinded study design. Methods: Patients with SPLs undergoing trans-gastric EUS fine needle aspiration (EUS-FNA) from July 2013 to March 2014 were prospectively enrolled. The nCLE diagnoses were compared with the final diagnoses. Researchers learned about the EUS-nCLE findings from previously published studies and applied it to diagnose SPLs. In the meantime, the findings were recorded. Results: In total, 22 patients were recruited (mean age 62.7 years, SD 13.8 years; 14 men and eight women). The mean maximal tumor diameter was 36.0 mm (SD 10.9 mm). EUS-nCLE yielded satisfactory images in all patients during the first EUS procedure and diagnosed benign and malignant SPLs in 3 and 19 patients, respectively. Final diagnoses of malignant SPLs were made in 19 patients. Benign SPLs were eventually diagnosed in three patients, with confirmed the cytology and disease stability during the 12-month follow-up period. At the end of the project, based on the results of this current study, EUS-nCLE findings for malignant SPLs were dark clumping with or without dilated vessels (> 40 μm). There were two criteria for diagnosing benign lesions which were white fibrous bands and normal acini cells. The accuracy rate of EUS-nCLE was 90.9 % (20/22). One falsely diagnosed malignant SPL was an inflammatory mass from a recent acute pancreatitis. Another one with a pancreatic neuroendocrine tumor presenting with a symptomatic pseudocyst was incorrectly diagnosed as an inflammatory mass. This was likely from sampling error of the EUS-nCLE probe in an inflammatory area. Only one patient had post EUS-FNA bleeding but did not require a blood transfusion. The inter-observer agreement among three blinded endoscopists was almost perfect (Kappa 0.82). Conclusion: EUS-nCLE is a promising technique for the diagnosis of SPLs with good inter-observer agreement. Study registration‎: TCTR20140402001