Role of fluorescence confocal microscopy for rapid evaluation of EUS fine-needle biopsy sampling in pancreatic solid lesions

Background and aims: EUS fine-needle biopsy (EUS-FNB) sampling is the standard procedure for diagnosis of pancreatic lesions. Fluorescence confocal microscopy (FCM) allows imaging of tissues in the fresh state, requiring minimal preparation without damage or loss of tissue. Until now, no data exist on FCM in the field of microhistologic specimens. We aimed to assess the diagnostic performance of FCM in predicting histologic adequacy of EUS-FNB samples in pancreatic solid lesions and to assess the agreement between FCM evaluation and final histology. Methods: In this single-center prospective study on consecutive patients with pancreatic lesions receiving EUS-FNB, the obtained samples have been evaluated at FCM and classified as "inadequate" or "adequate" (benign, suspicious, or malignant). The kappa test was used to quantify agreement. The diagnostic accuracy of FCM was assessed. A P < .05 was considered to be statistically significant. Results: From April 2020 to September 2020, 81 patients were enrolled. In all cases FCM showed the macro image of the sample and created a digital image. Of the samples, 92.6% was defined as adequate at the FCM evaluation and confirmed at histopathology. Histologic diagnoses were 8% benign, 17.3% atypical/suspicious, and 74.7% malignant with satisfactory agreement with the FCM evaluation (Cohen's κ coefficient, .95; 95% confidence interval [CI], .89-1.01; P = .001). The sensitivity of the FCM evaluation was 100% (95% CI, 95%-100%), specificity 66.7% (95% CI, 22.3%-95.7%), accuracy 97% (95% CI, 90.7%-99.7%), positive predictive value 97% (95% CI, 91.8%-99%), and negative predictive value 100%. Conclusions: FCM represents a new technique successfully applicable to microhistologic specimens. It provides fast information about sample adequacy in small specimens with good agreement in the final histology.