Pancreatic intraductal papillary mucinous neoplasms: role of CT in predicting pathologic subtypes

The objective of our study was to evaluate whether CT can be used to predict the pathologic subtypes of pancreatic intraductal papillary mucinous neoplasms (IPMNs).

Three radiologists, blinded to the pathologic IPMN subtype, retrospectively and independently reviewed the preoperative CT scans of 38 patients with surgically resected pancreatic IPMN: 11 intraductal papillary mucinous adenomas, 11 intraductal papillary mucinous carcinomas, and 16 intraductal papillary mucinous carcinomas with invasion. The patients, 16 women and 22 men, ranged in age from 38 to 80 years (mean age, 64.3 years). CT findings were correlated with each pathologic subtype using the chi-square (two-sided) test and analysis of variance. Interobserver agreement of the CT diagnosis of pathologic subtype and agreement between the CT diagnosis and pathologic subtype were also studied (kappa statistic).

Predominant main pancreatic duct (MPD) involvement (p = 0.04) and a wide (> 1 cm) connection of a side-branch lesion with the MPD (p = 0.03) correlated with intraductal papillary mucinous carcinoma with invasion. Tumor size, MPD diameter, number of tumors per patient, number of pseudoseptations per tumor, common bile duct dilatation, enlarged lymph nodes, intraductal calcifications, papillary bulging, and presence and size of a solid mass yielded no statistically significant relationship with pathologic subtype. Both interobserver agreement of CT diagnosis (range, 0.004-0.359) and agreement between CT diagnosis and pathologic subtype (range, 0.046-0.317) ranged from slight to fair.

Prediction of the pathologic subtypes of pancreatic IPMNs by CT is limited. Predominant MPD involvement and a wide connection of a side-branch lesion with the MPD are the only CT findings that can be used to predict the pathologic subtype of pancreatic IPMN.