Pathology of the Pancreas

A study on the human pancreaticobiliary duct system and ampulla region with their clinical considerations

INTRODUCTION

The purpose of this study is to present the variations of the pancreatic duct system and hepatopancreatic ampulla so that an awareness of these variations may help in surgical planning and prevention of ductal injury.

METHODS

Forty human pancreatic specimens were used to study the duct pattern of the pancreas and the formation and mode of termination of the pancreatic ducts. Also, the patency of the main pancreatic ducts, length of the hepatopancreatic ampulla, and length of the main pancreatic duct were measured.

RESULTS

The main pancreatic duct was patent in 37 out of 40 specimens, 2 specimens showed the embryonic type of the duct system, and one had the duct obliterated at its duodenal end. The mode of termination of the main pancreatic and common pancreatic ducts was divided into four types. Seventy-five percent specimens belonged to type I, followed by type II in 22.5 % and type III in 2.5 % of specimens. The length of the main pancreatic duct ranged from 11 to 21.2 cm, the average being 17.3 cm, and the length of the hepatopancreatic ampulla varied from 1 to 10 mm (1 to 2 mm-5 %, 3 to 8 mm-55 %, and more than 8 mm in 15 % of specimens), and it was absent in 25 %.

CONCLUSION

Awareness of these anomalies may help in surgical planning and prevention of undue ductal injury.

Imaging techniques in pancreatic tumors

Conventional ultrasonography represents the first diagnostic imaging modality for the study of pancreatic tumors. Contrast-enhanced ultrasound has significantly improved the accuracy of first-line examination and may influence the choice of second-line investigations: multidetector computed tomography is considered the gold standard for studying pancreatic solid lesions and tumor staging, while MRI with magnetic resonance cholangiopancreatography allows better study of pancreatic cystic lesions and the ductal system. To definitely diagnose a pancreatic lesion, image-guided fine-needle-aspiration or biopsy are very often required. PET with 18-fluorodeoxyglucose, endoscopic ultrasound and intraoperative ultrasonography remain techniques often employed in the third line. This article reviews the imaging techniques generally used for diagnosing the main pancreatic tumors, and a work-up algorithm is finally proposed.

Contrast-enhanced ultrasound of the pancreas

The introduction of contrast-enhanced ultrasonography (CEUS) has led to major improvements in the diagnostic capabilities of ultrasound (US). The innovative use of CEUS for study of the pancreas has created the need for a definition of the most frequent dynamic features of solid and cystic masses. CEUS is less expensive compared to computed tomography and magnetic resonance imaging and is able to significantly improve the accuracy of US, allowing better characterization and staging of pancreatic pathologies.

Ultrasonography of the pancreas. 4. Contrast-enhanced imaging

The introduction of contrast-enhanced ultrasonography (CEUS) has lead to great developments in the diagnostic capabilities of ultrasound. Second generation contrast media, characterized by harmonic responses at low mechanical index of the ultrasound beam, have already proven usefulness in the study of the liver but other abdominal organs can take advantage from the dynamic study during continuous ultrasonographic scans. The dynamic observation of the enhancement allows the perfect evaluation of the abdominal organs perfusion. The perfusion of the pancreas is well correlated to the semeiology of the gland parenchymography at CEUS. The study of the pancreas is a new and promising application of CEUS. CEUS can be used to better identify pancreatic lesions respect to conventional Ultrasound (US) or to characterize pancreatic lesions already visible at US. Moreover the staging of some pancreatic lesions can be improved by the use of contrast media. This article will review the clinical application of CEUS in the different pancreatic pathologies.

[Pancreas. Part II: Tumors]

Adenocarcinoma is the most common malignant pancreatic tumor, affecting the head in 60-70% of cases. By the time of diagnosis, approximately 80% of tumors are unresectable. Helical CT is very effective in detection and staging of adenocarcinoma, with a sensitivity of 76-92% for detection and an accuracy of 80-90% for staging, but it has limitations in the detection of small cancers (< or =2 cm). Multidetector CT (MDCT) has brought substantial improvements with its inherent 3D imaging capability. Mangafodipir-enhanced MRI is a problem-solving tool in the depiction of small cancers following an equivocal CT imaging result. Gadolinium-enhanced 3D gradient-echo MRI is helpful in the assessment of vascular invasion of cancer and in determining the etiology of cystic lesions. Serous cystadenoma is benign, has a lobulated contour and contains innumerable small cysts of 0.1-2 cm in diameter. Mucinous cystic neoplasms are unilocular or multilocular (fewer than six cysts), and the cyst diameter exceeds 2 cm. The presence of solid nodular components should alert the radiologist to suspect cystadenocarcinoma. Neuroendocrine tumors are mostly hypervascular. Diagnosis of insulinoma is a challenge: they are <2 cm in 90% of cases and mostly hypervascular at CT or MRI. A combination of contrast-enhanced MDCT, MRI, endosonography, and/or somatostatin receptor scintigraphy is used to detect these small tumors. This review summarizes the imaging features of the most common pancreatic tumors and discusses the limitations of CT, MRI and endosonography.

Preoperative evaluation of intraductal papillary mucinous tumors performed by pancreatic magnetic resonance imaging and correlated with surgical and histopathologic findings

PURPOSE

To evaluate the effectiveness of magnetic resonance imaging (MRI) in predicting the location, type of ductal involvement, and malignant transformation of intraductal papillary mucinous (IPM) pancreatic tumors made in a preoperative routine exam.

MATERIALS AND METHODS

A total of 24 patients with histologic confirmation of IPM tumor (IPMT) were included in this study. The MR images obtained in operation patients were retrospectively assessed. Two radiologists who were unaware of the initial interpretations of the images independently analyzed the MRI studies and characterized the type of lesions, location, and signs of malignant transformation. Interobserver agreement was determined with weighted kappa statistics. After consensus of both radiologists, the observer performances for the MRI interpretations were compared with surgical and histologic results using weighted kappa statistics and Fisher test.

RESULTS

At macroscopic examination, lesions were of combined type in 17 cases and of branch duct type in seven cases. At histologic analysis, three cases were classified as benign, three as borderline tumors, and 18 as carcinomas (eight in situ, 10 invasive). The lesions were located mainly in the head or uncinate process (N = 16) or were diffuse or multifocal (N = 2). Excellent agreement was found between the interpreters (0.90) in the evaluation of ductal involvement, good in the evaluation of lesion location (0.80) and in the diagnosis of malignant transformation (0.74). The correlation between MRI and histopathologic results was excellent in the evaluation of ductal involvement (0.90, sensitivity = 100%, specificity = 94%) and moderate in the evaluation of lesion location (0.57, sensitivity = 87%, specificity = 56%) and in the diagnosis of malignant transformation (0.60, sensitivity = 83%, specificity = 83%).

CONCLUSION

MRI is an effective method of characterizing IPMT in preoperative practice. The predictive sign of IPM pancreatic tumor malignancy at MRI included only the presence of solid mass or mural nodules.