Usefulness of Contrast-Enhanced Endoscopic Ultrasonography (CE-EUS) in the Diagnosis of Mural Nodule of Intraductal Papillary Mucinous Neoplasms of the Pancreas. The Comparison of the CE-EUS Findings with the Pathological Findings

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Background: Intraductal papillary mucinous neoplasms of the pancreas (IPMNs) vary histopathologically from benign to malignant lesions. Diagnostic and therapeutic strategies still remain unresolved in the international consensus guidelines for management of IPMNs, (proposed on 2006). The purpose of this study is to define “mural nodules” by the comparison of CE-EUS findings with the pathological findings. (Patients and Methods) Two hundred ninety-four patients with IPMNs examined by CE-EUS as the initial diagnostic modality since January, 2001 were enrolled. Eighty-seven cases were surgically treated. Our indications for resection were as follows: the case of main-duct type, existence of nodular projection “mural nodule” with blood flow signal in CE-EUS and coexistence of ductal cancer cases. We classified “mural nodule” into 4 types on the basis of morphological EUS findings. Type1 (low papillary type): low papillary projection spreading along the cystic wall or main pancreatic duct. Type2 (polypoid type): polypoid projection with smooth surface sparsely existing. Type3 (villous type):thickened cyst wall or main duct with villous or irregular surface structure. Type4 (invasive type):.hypoechoic blurred area located between pancreatic parenchyma and lesions (Type1-3). Target lesions were observed by EUS, then, CE-EUS were examined to identify the “mural nodule” with color signals. . Contrast agent (Levovist; Schering, Japan) was injected intravenously, and enhancement effect (color Doppler flow imaging) was estimated. The endoscopes used were EG-3630UR/EG-3760URK (Pentax) and ultrasound systems were EUB-8500,HV-900 (Hitachi). (Results)Eighty seven patients were resected (main-duct type, 14; mixed type, 25; branch-duct type, 48). There were 42 with adenoma, 25 with carcinoma in situ, 16 with invasive carcinoma derived from IPMN, and 3 with coexistence ductal cancer and no hyperplastic case. Malignant cases were 11/14 (78.6%) in main-duct type, 14/25 (56.0%) in mixed type and 21/48 (43.8%) in branch-duct type. In comparison of CE-EUS findings with pathological findings, papillary projection observed by EUS represented the epithelial change at least 500-750μm in diameter . Malignant cases were Type1(25%), Type2 (38.5%), Type3 (93.1%),and Type4 (91.7%), respectively. When IPMNs with Type3/4 were diagnosed as malignant, accuracy was up to 75.9%. Conclusion: “Mural nodules” diagnosed by CE-EUS represents very fine epitherial changes in IPMNs. CE-EUS is very useful in the diagnosis of malignant potential and the distribution of IPMNs.