Diagnostic value of digital droplet polymerase chain reaction and digital multiplexed detection of single-nucleotide variants in pancreatic cytology specimens collected by EUS-guided FNA

Background and aims: EUS-guided FNA is recommended as a first-line procedure for the histopathologic diagnosis of pancreatic cancer. Molecular analysis of EUS-FNA samples might be used as an auxiliary tool to strengthen the diagnosis. The current study aimed to evaluate the diagnostic performances of K-ras testing using droplet digital polymerase chain reaction (ddPCR) and a novel single-nucleotide variant (SNV) assay performed on pancreatic EUS-FNA samples.

Methods: EUS-FNA specimens from 31 patients with pancreatic masses (22 pancreatic ductal adenocarcinomas, 7 chronic pancreatitis, and 2 pancreatic neuroendocrine tumors) were included in the study. K-ras testing was initially performed by ddPCR. In addition, mutational status was evaluated using an SNV assay by NanoString technology, using digital enumeration of unique barcoded probes to detect 97 SNVs from 24 genes of clinical significance.

Results: The overall specificity and sensitivity of cytologic examination were 100% and 63%, respectively. K-ras mutation testing was performed using ddPCR, and the sensitivity increased to 87% with specificity 90%. The SNV assay detected at least 1 variant in 90% of pancreatic ductal adenocarcinoma samples; the test was able to detect 2 K-ras codon 61 mutations in 2 cases of pancreatic ductal adenocarcinoma, which were missed by ddPCR. The overall diagnostic accuracy of the cytologic examination alone was 74%, and it increased to 91% when the results of both molecular tests were considered for the cases with negative and inconclusive results.

Conclusions: The current study illustrated that integration of K-ras analysis with cytologic evaluation, especially in inconclusive cases, can enhance the diagnostic accuracy of EUS-FNA for pancreatic lesions.