Rapid growth speed of cysts can predict malignant intraductal mucinous papillary neoplasms

Abstract Background Branch duct intraductal papillary mucinous neoplasm (BD-IPMN) has the potential for malignant transformation. Current risk factors used to predict malignant transformation, such as mural nodules and cyst size > 30 mm, are insufficient. Therefore, we aimed to investigate the predictive significance of cyst growth speed. Materials and methods Between 2006 and 2017, 102 patients underwent pancreatectomy for IPMN. Of these, 50 patients with pathologically diagnosed BD-IPMN were selected for cyst growth analysis. Cyst growth speed, total cyst growth, and cyst growth rate were calculated retrospectively using the maximum diameter of the cyst at the first diagnosis and images taken preoperatively. Results Of the 50 BD-IPMN cases, 33 were diagnosed as benign (low to intermediate dysplasia) and 17 were malignant (10 high-grade dysplasias and seven invasive carcinomas). While no significant differences were observed in the presence of enhancing mural nodules or cyst size, malignant IPMN grew at a significantly faster speed (5.7 versus 1.6 mm/y; P versus 3.1 mm; P  = 0.015), and greater percentage of cyst diameter (28.5% versus 9.5%; P  = 0.006) than those of benign IPMN. Receiver operator characteristic curve analysis indicated that cyst growth speed had the greatest predictive performance among these three factors. Cyst growth speed > 3.5 mm/y was demonstrated to predict malignant IPMN with a sensitivity of 88% and specificity of 91%. Conclusions Cyst growth speed > 3.5 mm/y may be a good predictor for malignant IPMN. It can improve the diagnostic accuracy and optimize surgery for BD-IPMN.