Intraductal Papillary Mucinous Neoplasms: Imaging Features With Pathologic Correlation

Intraductal papillary mucinous neoplasms (IPMNs) are uncommon pancreatic cystic tumors arising from the columnar epithelial cells of pancreatic duct, comprising approximately 10-15% of all pancreatic cystic neoplasm. These tumors are most frequently identified in the elderly (60-80 years of age) with a male predilection. Recently, as being recognized gradually, IPMNs present with an increasing incidence in population. Pathohistologically, IPMNs are characterized by secreting large amounts of mucus and being papillary in growth pattern, and can be further divided into atypical hyperplasia, carcinoma in situ and invasive carcinoma according to its microscopic appearance. With the significant risk to evolve into invasive cancer, it is generally considered IPMNs should undergo resection, even in patients who are asymptomatic. Since coexisting chronic pancreatitis due to mucus obstruction of the pancreatic duct is common in patients with IPMNs, sometimes clinical presentation can hardly distinguish them from chronic pancreatitis with repeated acute exacerbations. At present, it is considered that cross-section imaging modalities including computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography (US), et al, plays an important role in the preoperative diagnosis of IPMNs. This study was intended to elucidate the clinical presentations, pathologic and imaging features of IPMNs, and to further improve the awareness and diagnostic level of this condition.PartⅠ:Diagnostic value of CT in pancreatic intraductal papillary mucinous neoplasmsTo evaluate the role of spiral CT in diagnosis of intraductal papillary mucinous neoplasms (IPMNs) of pancreas. Methods:To retrospectively determine the accuracy of CT images combined with clinical manifestation, with histopathologic analysis as the reference standard. A total of 50 patients (age range,32-87 years, mean age,61 years) with histopathologically proved IPMNs were enrolled in the study, including 34 men and 16 women. Results:Among the total 50 patients with IPMNs, most (n=28,56%) were elderly (>60 years). The primary symptoms were abdominal pain with or without pancreatitis. At CT images analysis,20 (35.7%) cases were interpretated as IPMNs of the main pancreatic duct(MPD);21(25%)as IPMNs of the side branches; and 9(39.3%) as IPMNs of the both the MPD and the side branches(mixed type). At histopathologic examination of the surgical specimen,28 of the 50 IPMNs were classified as adenomas,5 were classified as borderline tumors,9 were classified as carcinomas, and 8 were classified as carcinomas with invasion. Of the 22 malignant (borderline and carcinomas) IPMNs,3 had pancreatic calcification,3 had lymph metastasis,5 had capillary invasion, and 2 had liver metastasis. The malignant IPMNs mainly occured in MPD or mixed type (n=14), whereas side branch IPMNs were mostly benign (n=18).The diameter of the main pancreatic duct≤1.0cm and maxium diameter of the tumor≤4.0cm, with were considered to be the predictors of malignancy, more mural nodules were observed in the malignant than in the benign group. Conclusion:At the relatively specific features in image, the presence or absence of mural nodules, the diameter of the main pancreatic duct and the size of the tumor may help differentiate the malignancy from benignancy of IPMNs, CT is of great value in diagnosing, classifying and predicting malignancy of IPMNs.Part II:Intraductal Papillary Mucinous Neoplasms:Comparison Study between MRCP and ERCPObjective:To investigate the diagnostic value of MRCP and ERCP for the pancreatic intraductal papillary mucinous neoplasms (IPMNs), and to elucidate the imaging features of IPMNs. Method:From March 2005 to July 2009,39 cases of surgically proven intraductal papillary mucinous neoplasms (27 males and 12 females; aged 42 to 85 years, mean 61.8 years) were included into this study. Before operations, all of them had received MRCP and ERCP examination, and their clinical, MRCP, and ERCP data were analyzed. Results:Abdominal pain and pancreatitis were main clinical manifestations in pancreatic intraductal papillary mucinous neoplasms.39 IPMNs comprised 16 cases of main-pancreatic-duct type,17 cases of branch-duct type and 6 cases of mixed type. Among them,25 and 14 cases were respectively identified as pancreatic intraductal papillary mucinous adenoma and adenocarcinoma. Malignant rate in main-pancreatic-duct and mixed type was significantly higher than that in branch-duct type. In MRCP, the IPMNs of main-pancreatic-duct type presented with a diffuse or segmental dilation of main pancreatic duct, with mural nodules in 5 cases (5/16); Branch-type IPMNs were demonstrated as grape bunch-shaped or single cystic tumors, with mural nodules in 4 cases (4/17); Mixed-type IPMNs presented with both main pancreatic duct dilation and cystic tumor, with mural nodules in all 6 cases of lesions (6/6). MRCP distinctly revealed the traffic between the main pancreatic duct and lesions in 17 cases of branch-type IPMNs. ERCP mainly took the advantage in depicting the enlargement of duodenal papilla, mucus overflow and the main pancreatic duct dilation in varying degrees, and sometimes in revealing pancreatic head cystic lesions. However, most of the pancreatic tail were showed unclear or disappeared in ERCP. Detected ratio of IPMNs in ERCP and MRCP were 87% and 100%, respectively. Conclusion:ERCP can be directly displayed the overflow of jelly-like mucus from the enlargement of the duodenal papilla, the traffic between the lesions and main pancreatic duct, and filling defect within the lesion. MRCP is of more meaningful in the diagnosis of branch-type pancreatic intraductal papillary mucinous neoplasms. Compared with ERCP, MRCP is a non-invasive diagnostic tool for pancreatic intraductal papillary mucinous neoplasms.