Utility of EUS-guided Microbiopsies Combined With Auxiliary Molecular Techniques in the Workup of Pancreatic Cystic Lesions

Pancreatic ductal adenocarcinoma (PDAC) accounts for 6% of all cancer related deaths in Denmark, and the 5-year survival rate is only 8%. PDAC develops from precursor lesions with pancreatic intraepithelial neoplasia (panIN) being the most common, and cystic lesions as a second precursor. Unlike panINs, which are too small for detection with current imaging modalities, cystic lesions of the pancreas are increasingly diagnosed due to the extended use of cross-sectional imaging. Pancreatic cystic lesions may be observed in up to 13.5% of all MRI scans and 3% of all CT scans. There are several types of pancreatic cysts and each of them requires individual management, ranging from no treatment over watchful waiting to surgical resection according to their malignant potential.

Standard diagnostic workup includes cross-sectional imaging of the cystic lesions and, in selected cases endoscopic ultrasound (EUS) with aspiration of cyst fluid by fine needle aspiration (FNA), followed by cyst fluid cytology and tumor marker analysis. The diagnostic algorithm is based on International consensus guidelines established in 2006, and revised in 2012 and 2017, integrating clinical features with EUS-findings. The level of evidence in these guidelines is unfortunately low. A recent meta-analysis concluded that EUS and cyst fluid cytology have low sensitivity (54-63%), whereas the specificity is acceptable (88-92%) for detection of mucinous cysts. Low sensitivity is mainly due to absence of sufficient cellular material in the cyst fluid for definite diagnosis. Tumor marker analysis of cyst fluid, such as carcinoembryonic antigen (CEA), CA 72.4, CA 125, CA 19.9, and CA 15.3, have been studied extensively with CEA being the most accurate marker. A cut-off value of 192 ng/mL for CEA distinguishes mucinous from non-mucinous cysts with a good, albeit imperfect, accuracy of 80%. However, the value will not differentiate between IPMN and MCN, and more importantly, it does not correlate with the level of dysplasia or malignancy.

EUS-guided through-the-needle microbiopsy using the Moray™ forceps is a novel adjunctive. The device can be inserted through a EUS-FNA needle and used to obtain microbiopsies from different tissues in relationship to the gastrointestinal system. This instrument can be used in combination with EUS-FNA to subsequently obtain microbiopsies from the pancreatic cyst wall. Microbiopsies seem to represent a break-through in pre-operative classification of pancreatic cysts, as they provide histological material for examination of tissue architecture not readily accessible in FNA material. However, very little experience has been obtained hitherto. Even though this technique is currently described only in a few studies, it seems feasible and theoretically offers a higher quality of material than what can be obtained by EUS-FNA alone.