Assessment of the Usefulness of SMI (Superb Vascular Imaging) for the Characterisation of Pancreatic Cystic Tumours (IMAKYST)

Pancreatic cysts are becoming increasingly common in the general population. They are most often discovered incidentally during cross-sectional abdominal imaging.

There are different types of pancreatic cystic lesions, each with distinct risks of progression. Lesions with the potential for malignant transformation are typically mucinous lesions (papillary intraductal mucinous neoplasms of the pancreas [PIMN] and mucinous cystic neoplasms [MCN]), formerly known as mucinous cystadenomas), whereas non-mucinous lesions (serous cystadenomas [SCs] and pseudocysts) are entirely benign and do not require monitoring.

SC typically presents as a solitary cyst with no communication with the Wirsung duct, appearing microcystic with central calcification. This typical appearance is not always present, and SC can mimic a mucinous lesion. In such cases, imaging and echoendoscopy findings are not discriminatory. Histological and biochemical analysis of the fluid obtained during cyst aspiration may be helpful, but the specificity is usually insufficient to make a definitive decision regarding the absence of surgery and the need for monitoring. These diagnostic difficulties mean that one in three patients with SC undergo unnecessary surgery, with significant morbidity and mortality.

There are currently two highly effective techniques for diagnosing SC:

• Endocystic microbiopsy, which has a diagnostic accuracy of nearly 100% but a high complication rate (around 10%). It is no longer recommended except in exceptional cases.
• Needle-based confocal laser endomicroscopy (nCLE), which has 100% specificity for the diagnosis of SC.

SC is a lesion characterised by intense microvascularisation present in all the cyst walls and throughout the entire peripheral capsule of the cyst. SMI is a new ultrasound modality capable of visualising microvascular flow without the need for contrast injection, unlike nCLE.

The Mermoz Endoscopy Centre will be equipped with an ultrasound console enabling SMI to be performed during an echoendoscopy examination. This technology is now available on the new Aplio i800 EUS console (Canon-Olympus).

To date, no data has been published on the potential of SMI for characterising and diagnosing SC. This is why this clinical investigation is being conducted.

Inclusion criteria

• Patient referred for confocal microscopy (nCLE) assessment of a pancreatic cyst of unknown origin
• Patient with a cyst measuring more than 15 mm in diameter and at least one cyst cavity measuring ≥ 5 mm (to allow nCLE to be performed)
• Patient registered with or covered by the National Health Service
• French-speaking patient who has signed an informed consent form

Exclusion criteria

• Patient with calcifying chronic pancreatitis
• Presence of a communication with the main pancreatic duct on MRI or endoscopic ultrasound
• Patient whose lesion meets criteria for malignancy (tissue mass, metastases, ascites, vascular infiltration)
• Patient with a contraindication to endoscopic ultrasound-guided puncture (haemostatic disorder)
• Patient with a known allergy to fluorescein (used in nCLE)
• Pregnant woman
• Patient under legal guardianship: adults under guardianship, curatorship or other legal protection, or deprived of their liberty by judicial or administrative order
• Hospitalised patient without consent