It is not necessary to resect all mucinous cystic neoplasms of the pancreas: current guidelines do not reflect the actual risk of malignancy

Background: Mucinous Cystic Neoplasms (MCN) of the pancreas are premalignant cysts for which current guidelines support pancreatic resection. The primary aim of this systematic review and metaanalysis is to define the pooled rate of malignancy for MCN. Methods: A systematic review of eligible studies published between 2000 and 2021 was performed on PubMed and Embase. Primary outcome was rate of malignancy. Data regarding high-risk features, including cyst size and mural nodules, were collected and analyzed. Results: A total of 40 studies and 3292 patients with resected MCN were included in the final analysis. The pooled rate of malignancy was 16.1% (95%CI 13.1-19.0). The rate of malignant MCN in studies published before 2012 was significantly higher than that of studies published after recent guidelines were published (21.0% vs 14.9%, p < 0.001). Malignant MCN were larger than benign (mean difference 25.9 mm 95%CI 14.50-37.43, p < 0.001) with a direct correlation between size and presence of malignant MCN (R2 = 0.28, p = 0.020). A SROC identified a threshold of 65 mm to be associated with the diagnosis of malignant MCN. Presence of mural nodules was associated with the diagnosis of a malignant MCN (OR = 4.34, 95%CI 3.00-6.29, p < 0.001). Conclusion: Whereas guidelines recommend resection of all MCN, the rate of malignancy in resected MCN is 16%, implying that surveillance has a role in most cases, and that surgical selection criteria are warranted. Size and presence of mural nodules are significantly associated with an increased risk of malignant degeneration, small MCN and without mural nodules can be considered for surveillance.