Intraductal papillary mucinous neoplasms with associated invasive carcinoma of the pancreas: imaging findings and diagnostic performance of MDCT for prediction of prognostic factors

Abstract

Objective: The purpose of this study was to assess the diagnostic accuracy of MDCT for determining the prognostic factors, including the T category, lymph node metastasis, tumor size, and perineural invasion, in surgically proven intraductal papillary mucinous neoplasms (IPMNs) with an associated invasive carcinoma (IPMC) and to investigate the imaging findings.

Materials and methods: Our study group consisted of 38 patients with surgically proven IPMC who underwent preoperative dynamic CT. Two radiologists retrospectively assessed the morphologic type of IPMN, size of the cyst, size of the main pancreatic duct, and presence or absence of mural nodules. The radiologists also assessed the T category, lymph node metastasis, and perineural invasion. They graded the perineural invasion using a 3-point scale as follows: 1, normal; 2, streaky and strandlike structure in fat tissue as well as a fine, reticular pattern; and 3, irregular masses adjacent to the lesions. Statistical analyses were performed using receiver operating characteristic analysis, the McNemar test, and Fisher exact test. Kappa statistics were used to determine interobserver agreement.

Results: The morphologic types of IPMC included the main-duct type (n=11, 29%), combined type (n=18, 47%), and branch-duct type (n=9, 24%). The diagnostic accuracy for the T category was 73.7% (n=28) and 68.4% (n=26) and for the lymph node metastasis was 68.4% (n=26) and 76.3% (n=29), respectively, for the two readers, with moderate interobserver agreement (κ=0.636 and 0.708). The areas under the receiver operating characteristic curve for perineural invasion were 0.868 and 0.821. The sensitivity, specificity, and positive predictive value were 100%, 71.4%, 55.5%, and 90%, 71.4%, 52.9%, respectively. Interobserver agreement was moderate (κ=0.659). The tumor size seen on CT was not statistically different from the tumor size determined on pathology (3.9±[SD] 2.7 cm vs 3.8±2.1 cm, p=0.582). The main duct size was 11.5+6.2 mm. Mural nodules were detected in 74% (n=28) of our study patients.

Conclusion: CT might be useful for preoperatively evaluating the T category, lymph node metastasis, tumor size, and perineural invasion of IPMC. Main pancreatic duct dilatation and the presence of mural nodules are common findings of IPMC.