Volumetric and morphological analysis of intraductal papillary mucinous neoplasm of the pancreas using computed tomography and magnetic resonance imaging.

OBJECTIVE: The purpose of this study was to predict the malignancy of intraductal papillary mucinous neoplasm (IPMN) based on data obtained by computed tomography and magnetic resonance imaging. METHODS: Sixty-nine patients with IPMN underwent computed tomography, magnetic resonance imaging, and surgery. The tumors were classified pathologically as IPMN (adenoma), IPMN (in situ carcinoma), and invasive carcinoma derived from IPMN, and analyzed morphologically for the following characteristics: tumor size, main pancreatic duct (MPD) diameter, tumor area, MPD area, tumor volume, MPD volume, and intraductal volume (tumors volume + MPD volume). RESULTS: Main pancreatic duct diameter (P = 0.017) and intraductal volume (P = 0.0013) showed significant differences among IPMN (adenoma), IPMN (in situ carcinoma), and invasive carcinoma derived from IPMN. When IPMN (in situ carcinoma) and invasive carcinoma derived from IPMN were classified as malignant IPMN, an MPD diameter of 6 mm or more and an intraductal volume of 10 cm or more were set as cutoff levels predictive of malignancy using receiver operating characteristic curve analysis. On the basis of these criteria, the sensitivity and specificity for identifying malignancy in MPD were 83% and 59%, and those for intraductal volume were 70% and 73%, respectively. CONCLUSION: Intraductal volume (≥10 cm) determined by volumetric analysis is useful for diagnosis of malignant IPMN.

A pancreatobiliary-type carcinoma in situ at the periphery of a mural nodule developed from a gastric adenoma in an intraductal papillary mucinous neoplasm.

We report a rare case of an intraductal papillary mucinous neoplasm (IPMN) with a pancreatobiliary-type carcinoma in situ (CIS) that originated around a mural nodule formed in a gastric-type adenoma. A 64-year-old man was admitted to our hospital in December 2001 for dilation of the main pancreatic duct, detected on abdominal ultrasonography. Branch-duct-type IPMN (diameter 25 mm) was diagnosed, and because mural nodules were absent, the patient was annually followed up for 5 years. In 2006, computed tomography scans revealed thickening of the tumor wall and the development of a mural nodule (diameter approximately 6 mm); pancreatoduodenectomy with regional lymph-node dissection was performed. Histopathologic examination showed an intraductal papillary mucinous carcinoma arising from an adenoma. Hematoxylin and eosin (H&E) staining revealed that most of the tumor components, including the mural nodule, had adenomatous changes, indicating the tumor to be of the gastric type; however, immunohistochemistry showed positive MUC2 expression. Histologically, the tissues around the nodule, including those showing a cribriform pattern, were diagnosed as CIS. These tissues were classified as the pancreatobiliary-type on the basis of the results of both H&E staining and immunohistochemistry. The patient remained disease-free for 3 years after surgery.