Diagnostic accuracy of confocal laser endomicroscopy for the ex vivo characterization of peritoneal nodules during laparoscopic surgery

Background: Intraoperative characterization of peritoneal nodules can be challenging. Probe-based confocal laser endomicroscopy (pCLE) is an innovative technique enabling real-time microscopic analysis. This study aimed to assess the role of pCLE in the discrimination of benign versus malignant peritoneal nodules during laparoscopic staging. Materials and methods: During this prospective trial, pCLE was performed ex vivo on fresh samples of peritoneal nodules in 30 consecutive patients, after topical application of indocyanine green. The final diagnosis was obtained histologically, as per standard of care. pCLE image criteria for normal versus inflammatory versus malignant nodules were established (phase I); these criteria were tested retrospectively on selected videos by two examiners (phase II). The primary endpoints were values of accuracy in diagnosing malignant nodules. Results: pCLE criteria for malignant nodules defined in phase I were: strongly fluorescent irregular clusters of cancerous cells, nonfluorescent nuclei of cancerous cells, and substantially lower fluorescence of the extracellular matrix fluorescence compared with cancerous clusters. In phase II, the detection rate of these criteria was significantly higher in malignant compared with benign nodules. Overall sensitivity, specificity, positive and negative predictive values to detect malignant nodules were 75, 100, 100 and 89 %, respectively. Interobserver agreement was substantial (kappa 0.69). Conclusion: These preliminary results suggest that pCLE is a valuable tool to discriminate between benign and malignant peritoneal nodules, with a high positive predictive value.