Pancreatic cyst fluid harboring a KRAS mutation

Abstract

A 55-yr-old woman presented with abdominal bloating for approximately 1 year. Imaging studies showed a cyst in the body of the pancreas with proximal pancreatic ductal dilation. An endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) was performed. Cytologic findings from the cyst fluid were consistent with a mucinous neoplastic cyst, and the possibility of malignancy could not be entirely excluded. A KRAS mutation analysis was performed on the cyst fluid using the Idylla system and circulating tumor KRAS (ctKRAS) cartridge (Biocartis, Mechelen, Belgium), which tests for actionable mutations in exons 2, 3, and 4 of the KRAS gene. Idylla testing detected a KRAS G12D mutation in the cyst fluid. The patient subsequently underwent a distal subtotal pancreatectomy with splenectomy. Microscopic examination of the resected tissue revealed an intraductal papillary mucinous neoplasm (IPMN) with an associated invasive carcinoma. KRAS testing on the resected tumor tissue confirmed the G12D mutation detected in the cyst fluid earlier. The described rapid testing of KRAS directly from the pancreatic cyst fluid can complement cytology assessment to classify pancreatic cysts more reliably and can potentially be of significant help when other cyst findings are nondiagnostic.

Keywords: pancreatic cysts.

Figure 1.

(A) Endoscopic ultrasound (EUS) showing a 29-mm septated cystic lesion seen in the pancreatic body, associated with upstream ductal dilation. The outer wall of the lesion was thin. There was no associated mass. (B) Mucinous/gastric foveolar-type epithelial cells in a small cluster. (C) Focal cytologic and architecture atypia and background necrosis. (D) Cell block showing a few clusters of mucinous/gastric foveolar-type epithelial cells and background necrosis. (E) Cyst at the body of pancreas measuring 4.1 × 2.2 × 2.0 cm with solid area extending into the pancreatic duct (arrow). (F) IPMN (arrowhead) with an associated invasive carcinoma (arrow). (G) Invasive carcinoma with perineural invasion (arrow).