Pancreatic carcinoma is among the malignant tumours with the highest mortality and remains associated with an extremely poor prognosis. Early identification and surveillance of premalignant lesions, such as intraductal papillary mucinous neoplasms (IPMNs), are therefore of central importance for preventing malignant transformation. According to the current Kyoto Guidelines, for small branch-duct IPMNs (BD-IPMNs) measuring less than 20 mm and lacking high-risk factors (“worrisome features”), endoscopic ultrasonography (EUS) surveillance every 18 months is recommended. However, it remains unclear whether BD-IPMNs smaller than 10 mm carry a comparable risk of progression and therefore require monitoring at the same interval. The aim of this study is to evaluate whether BD-IPMNs smaller than 10 mm exhibit a similar risk for the development of “worrisome features” as BD-IPMNs measuring between 10 and 20 mm.

In this retrospective analysis, all patients who had undergone at least two endoscopic ultrasound (EUS) examinations at St. Josef-Hospital Bochum between January 1, 2006, and September 30, 2025, were identified based on the coded ICD diagnoses K86.2 (“pancreatic cyst”) or D37.70 (“neoplasm of uncertain or unknown behaviour: pancreas”). Data were collected from the clinical information system, and a total of 843 patients were identified.

As part of an ongoing project, 131 of the 843 identified patients have been fully evaluated to date. Among them, 47 patients (35.9%) presented with a BD-IPMN measuring <10 mm at the time of initial diagnosis. The mean follow-up period was 7.6 ± 3.3 years, with an average of 12.9 EUS examinations per patient. For comparison, 39 patients (29.8%) with BD-IPMNs measuring 10–20 mm were identified (mean follow-up period 7.0 ± 3.4 years; average of 13.4 EUS examinations). Lesions measuring 10–20 mm showed a 7.6-fold higher risk of developing “worrisome features” compared to lesions <10 mm (6.4% vs. 48.7%, p = 0.0005). The most common worrisome features in patients with lesions <10 mm were elevated CA19-9 levels (n=3), followed by cyst growth ≥2.5 mm per year (n=2). In contrast, the most common worrisome features in patients with BD-IPMNs measuring 10–20 mm were cyst growth ≥2.5 mm per year (n=14), followed by a main pancreatic duct diameter of 5–10 mm (n=6) and elevated CA19-9 levels (n=5).

The preliminary data indicate a significantly lower risk for the development of “worrisome features” in BD-IPMNs smaller than 10 mm compared to larger lesions (10–20 mm). In the extended analysis of the larger cohort, it will be assessed whether it is safe for this subgroup of patients to extend the surveillance interval or to omit further EUS follow-up.