Endoscopy 2011; 43 - A21
DOI: 10.1055/s-0031-1292092

Diagnostic accuracy and clinical utility of K-ras mutation analysis on FNA aspirates of pancreatic masses under EUS guidance

C De Angelis 1, M Goss 1, P Allegranza 1, F Brizzi 1, D Reggio 2, L Daniele 3, D Pacchioni 3, S Mariani 3, M Bruno 1, P Carucci 1, M Rizzetto 1
  • 1Department of Gastro-Hepatology, “S. Giovanni Battista – Molinette” Hospital, University of Turin, Italy
  • 2OLT Surgery, “S. Giovanni Battista – Molinette” Hospital, University of Turin, Italy
  • 3Department of Biomedical Sciences and Human Oncology, University of Turin, Turin, Italy

Introduction/Objectives: Cytological analysis on specimen obtained by Endoscopic Ultrasound-Fine NeedleAspiration (EUS-FNA) is known as the most accurate technique for the diagnosis of pancreatic adenocarcinoma. Nonetheless, differenzial diagnosis between adenocarcinoma and other pseudotumoral lesions (such as chronic pancreatitis) can be challenging. Almost all pancreatic adenocarcinomas show mutational activation of K-ras oncogene. Analysis of mutations of K-ras on aspirates provided by EUS-FNA could be a helpful method to distinguish neoplasia from benign lesions.

Aims & Methods: We analyzed cytologic specimens obtained by EUS-FNA from 63 patients showing suspicious pancreatic masses. A cytological analysis and the research of K-ras activating mutation on codon 12, using restriction endonuclease-mediated selective PCR (REMS-PCR), were performed. Assuming unequivocal cytology, surgical specimens and/or a proper follow-up as gold standards, 52 subjects were definitively diagnosticated as having adenocarcinoma, and 11 cases with other lesions (5 chronic pancreatitis, 4 neuroendocrine tumors, 2 metastatic lesions).

Results: REMS-PCR for K-ras point mutation analysis was successfully performed in all cases. Specific K-ras point mutations were present in 42/52 cases of adenocarcinoma. Mutations were also detected in 1/5 cases of chronic pancreatitis and in 1/4 neuroendocrine tumors. Sensitivity and specificity of K-ras mutations in detecting pancreatic adenocarcinomas were respectively 80.7% and 81%. In 14 patients the cytological diagnosis was difficult (low cellularity, minimal cell atypias, miss of atypical cells in strongly suspicious masses): in this subgroup K-ras mutations could help reaching a definitive diagnosis of malignancy with a positive and negative predicting value of respectively 87.5 and 66.6%.

Conclusion: K-ras oncogene analysis is a feasible technique with good sensitivity and specificity. In patients with doubtful cytology, the presence of K-ras mutations seems to be an helpful predictor of neoplasia.