Confocal laser endomicroscopy (CLE) is a novel and highly promising imaging method for that allows in vivo imaging of the mucosal layer at resolution of approximately 1 micron. Cellular and sub-cellular structures as well as capillaries and single red blood cells can be visualized. CLE is now well established as a highly accurate method for distinguishing neoplasia in the gastrointestinal tract lumen via endoscopy. A major new breakthrough is the development of sub-millimeter CLE probes that can be passed via an image guided needle (nCLE) into solid organs and cysts.

It is hypothesized that nCLE will help distinguish the benign, premalignant and malignant cystic lesions of pancreas by visualizing the cellular lining of the cysts, thereby, avoiding unnecessary surgery in patient with benign cysts and guiding to early and effective surgical removal of high risk neoplastic lesions.

A prototype minimal risk nCLE system has been developed that can be passed via standard endoscopic ultrasound needles into the pancreas but FDA clearance for in vivo use is not expected until late 2010. The investigators propose to evaluate this prototype nCLE system in vivo during endoscopic ultrasound (EUS), as an initial pilot study.

Hypothesis: the confocal laser endomicroscopy imaging of the nCLE can differentiate between non-mucinous, mucinous non- malignant and malignant pancreatic cysts in vivo and has increased sensitivity compared to endoscopic ultrasound-fine needle aspiration (EUS-FNA) tissue sampling. In this pilot study the investigators will primarily evaluate technical feasibility and interobserver agreement.

1. In patients undergoing EUS for suspected pancreatic cysts, the investigators will evaluate the key nCLE image features of non mucinous, mucinous, and malignant pancreatic cystic neoplasms (PCN).
2. The investigators will estimate the initial image quality, feasibility, and interobserver agreement of nCLE
3. The investigators will establish the preliminary accuracy of nCLE to be used for planning a larger comparative trial

Inclusion Criteria:

• Patients undergoing endoscopic ultrasound for evaluation of pancreatic cysts (including pseudocysts and suspected pancreatic cystic neoplasms) in the gastrointestinal (GI) lab at Mayo Clinic Jacksonville.

Exclusion Criteria:

• Unwilling/unable to consent;
• Solid pancreatic mass on computerized axial tomography/magnetic resonance (CT/MR);
• Allergy to Fluorescein;
• Pregnancy.