You are in: eMedicine Specialties > Radiology > GASTROINTESTINAL Pancreas, AdenocarcinomaArticle Last Updated: Apr 13, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Mahesh Kumar Neelala Anand, MBBS, DNB, FRCR, Clinical Director, Consultant Radiologist, Department of Radiology, Pennine Acute Hospitals NHS Trust, Manchester, UK Mahesh Kumar Neelala Anand is a member of the following medical societies: British Medical Association, Radiological Society of North America, and Royal College of Radiologists Coauthor(s): Colm Boylan, MRCP, FRCR, Specialist Registrar, Department of Radiology, North Manchester General Hospital NHS Trust, UK; Narainder Gupta, MD, DRM, MSc, FRCR, Division Director, Assistant Professor of Cardio-thoracic Radiology, Division of Cardiothoracic Radiology, Thomas Jefferson University Hospital Editors: Zahir Amin, MBBS, MRCP, MD, FRCR, Consulting Staff, Department of Imaging, The Middlesex Hospital, University College London Hospitals Trust; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Udo P Schmiedl, MD, PhD, Clinical Professor, Department of Radiology, University of Washington; Consulting Staff, Swedish Medical Center, University of Washington Medical Center, Seattle Radiologists; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; John Karani, MBBS, FRCR, Consulting Staff, Department of Radiology, King's College Hospital, London Author and Editor Disclosure Synonyms and related keywords: pancreatic exocrine tumor, pancreatic carcinoma INTRODUCTIONSection 2 of 12
  BackgroundOf all the GI malignancies, pancreatic adenocarcinoma is the second most common cause of death from cancer. In clinical practice, pancreatic cancer is synonymous with pancreatic ductal adenocarcinoma, which constitutes 90% of all primary malignant tumors arising from the pancreatic gland. Tumors may arise from pancreatic ducts (99%) or from acinar cells (1%). More than 90% of pancreatic cancers appear in the late stage of disease; this observation emphasizes the role of radiology in early detection and determination of resectability of the tumor. The role of diagnostic imaging is to demonstrate the tumor and its relationship to surrounding vasculature, and the results determine the possibility of curative resection. The diagnosis of pancreatic cancer is rarely made at an early stage. This is one of the main reasons for failing to achieve a cure in most patients. For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education article Pancreatic Cancer. Epidemiology and etiology The definitive causative factors that indicate an increased incidence of pancreatic cancer are unknown. High-protein and high-fat diets, cigarette smoking, and exposure to industrial carcinogens are implicated as causative factors. An increased incidence has been reported in chemists, workers in metal industries, and coke- and gas-plant employees. Hereditary pancreatitis is present in 40% of patients with pancreatic carcinoma. Cigarette smoking increases the risk by 2 times and diabetes by 2 times more than the general population. Alcohol abuse is seen in 4% of patients. Asbestos exposure is not associated with pancreatic carcinoma. Undoubtedly, an association exists between pancreatic cancer and diabetes mellitus. Association of alcohol and pancreatic cancer is indirectly related to the development of alcohol-induced pancreatitis. The acquired variety of chronic pancreatitis does not seem to be strongly related to pancreatic cancer. Individuals with the hereditary type of chronic pancreatitis seem to have a predisposition for pancreatic cancer stronger than that of the general population. PathophysiologyPathologically, the adenocarcinomas may be classified as follows:
Most of the tumors produce mucin (75%) and are located in the head of the pancreas. FrequencyUnited StatesPancreatic cancer is the fifth leading cause of cancer deaths in the United States. Approximately 28,000 new pancreatic cancers are diagnosed in the United States each year. Of the affected patients, 60% have liver metastasis, malignant ascites, or other evidence of tumor spread at the time of diagnosis. InternationalThe incidence of cancer has tripled over the past 40 years throughout the Western world. It is highly fatal and has one of the lowest survival rates. In England and Wales, pancreatic cancer accounts for approximately 6000 deaths each year. Mortality/MorbidityIn the United States, pancreatic cancer accounts for an estimated 8.4 deaths per 100,000 persons. Adenocarcinoma of the pancreatic head has a 3-year survival rate of only 2%, and the 5-year survival rate after resection is about 20%. The overall survival rate is 0.5%. Approximately 80-90% of patients have regional and distant metastases by the time the disease is diagnosed and are not suitable for curative resection. Only 4-16% of the tumors are resectable at diagnosis. Currently, as many as 30% of patients who are referred for surgery on the basis of their CT findings are discovered to be unsuitable candidates. In most patients, even palliation cannot be achieved because of advanced disease at presentation. Overall, fewer than 5% of patients undergo resection, but among these, as many as 20% survive 5 years. The median survival is less than 18 months after surgery. SexPancreatic cancer is more common in men than in women. The male-to-female ratio has been decreasing recently, suggesting that more women are developing the malignancy. AgeThose aged 60-80 years are most affected. Pancreatic adenocarcinoma is uncommon but not rare in those younger than 55 years. It is uncommon in those younger than 40 years. AnatomyThe pancreas is divided into head, neck, body, and tail segments for descriptive purposes, and it lies in the retroperitoneum within the anterior pararenal space. The head is the portion of the gland lying within the C-loop curve of the duodenum. The head is prolonged inferiorly and medially to extend behind the superior mesenteric vein. The uncinate process usually stops short at the level of the right renal hilum inferiorly. The neck of the gland is the constricted segment of the gland lying anterior to the superior mesenteric vessels. The body is a horizontal segment of the gland lying behind the lesser sac and stomach. Dorsal to the body runs the splenic vein. The tail of pancreas may be slightly cephalic to the level of the head. It follows the splenic vessels into the splenic hilum. The main pancreatic duct (duct of Wirsung) opens at the major duodenal papilla, measuring 3-4 mm in diameter in adults. It enlarges slightly with advancing age. The diameter of the duct tapers to 1-2 mm toward the tail. A slight narrowing at the head and body of the pancreas is a normal variation. The accessory pancreatic duct (duct of Santorini) opens at the minor duodenal papilla, proximal to the major duodenal papilla. The 2 ducts join in the head of pancreas in 90-95% of patients. In 20-30% of patients, the accessory duct retains a patent orifice at the minor papilla. Small side branches that are delicate, tapering, and gracile originate at approximately right angles to the main duct throughout the length of the gland. A prominent side branch seen as common normal variations include one from the midbody and another from the uncinate process. On cross-sectional images, the measurements of normal pancreas diameters generally are as follows: head of the pancreas, 3 cm; neck and body of the pancreas, 2.5 cm; and tail, as long as 2 cm. The position, size, and shape of the pancreas vary among patients. The pancreas gradually diminishes with advancing age, sometimes becoming more marked beyond the seventh decade. The surface of the pancreas is smooth in 80% of patients and lobulated in approximately 20%. Clinical DetailsClinical symptoms and signs develop late and depend on the site of the tumor. Tumors in the body and tail produce late symptoms. Pain is the most consistent symptom. Painless jaundice alone is uncommon and is seen in 13% of patients. Approximately 34% present with pain alone, and about 46% with pain and jaundice. Severe pain invariably indicates spread of tumor to perineural lymphatics. Weight loss and anorexia are observed in 7% of patients. Hematemesis and melena occasionally occur in late cases, and these may be caused by direct invasion of the adjacent duodenum or stomach or as a result of portal hypertension from splenic and portal vein obstruction. Physical examination A palpable gall bladder (Courvoisier sign) is observed in approximately 25% of patients with operable tumors. Tumors in the body and tail appear late, as they do not cause any immediate pressure effects on ducts. They present with pain when large. Hepatomegaly is seen in 65% of patients and may indicate liver metastasis, although the sign is nonspecific. Positive clinical signs indicate incurable disease, and a palpable abdominal mass is observed in 10% and ascites in 5%, which suggests advanced disease. Obstructive jaundice is seen in 75% of patients. Other signs include new onset of diabetes in 25-50% of patients, thrombophlebitis, and fatigue. More than 90% of patients present at a late stage in the disease process. Laboratory tests reveal elevated bilirubin concentrations. The total bilirubin level tends to be greater with malignant obstruction, as compared with the increase in bilirubin levels due to ductal obstruction caused by choledocholithiasis (mean levels of 15 vs 5 mg/dL). Conjugated bilirubin and alkaline phosphatase levels are higher in patients with obstructive jaundice than in those with liver parenchymal disease. Elevation of serum amylase values is less common and seen in about 5% of patients with pancreatic cancer. Staging American Joint Committee for Cancer (AJCC) staging of carcinoma of the pancreas is as follows:
Preferred ExaminationThere is much debate concerning the sensitivity and specificity of imaging investigations in the diagnosis and staging of pancreatic carcinoma. Multisection CT is generally accepted to be the first line of investigation in a patient with suspected pancreatic cancer. The best imaging technique is determined by local availability and expertise, but this will nearly always be spiral CT (ideally multisection CT). The reasons for this preference include its wide availability, speed, thin sections, optimal enhancement, high spatial resolution, and consistently good images. The importance of good CT technique cannot be overemphasized, and the key elements are the following: oral water as negative intraluminal contrast, 120-150 mL of iodinated contrast material intravenously administered at a rate of 3-4 mL/s, and scanning with thin (2- to 3-mm) collimation during pancreatic parenchymal phase (at 25-35 s) with the liver phase obtained at 60-70 s. If the patient is clinically jaundiced and when biliary ductal dilatation is demonstrated on ultrasonographic (US) examination, endoscopic retrograde cholangiopancreatography (ERCP) is the next investigation of choice with a view to a drainage procedure. ERCP reliably demonstrates the point of obstruction. US is often the initial test in symptomatic patients. US is used for diagnosis rather than staging, although liver metastasis and ascites may be seen. Significant technical improvements in US have occurred. It may be used for problem solving in thin patients. Portal venous involvement may be more apparent on sonograms than on CT and/or MRI images, and liver lesions can be characterized as cystic or solid. MRI has improved considerably in recent years, and it continues to evolve. Studies comparing CT and MRI found that detection and assessment of resectability to be similar with both modalities. MRI takes longer, it costs more, it is more complex, and it is limited by artifacts. The current role of MRI is probably problem solving. That is if the mass is not demonstrable with CT and US, MRI could be used to evaluate the pancreas in obstructive jaundice. MRI is also helpful in evaluating and characterizing liver lesions in patients with pancreatic cancer. In the detection and staging of small tumors, endoscopic US (EUS) can be reliable when it is performed by experienced imagers. Previous studies have demonstrated a higher sensitivity and specificity with EUS than with other modalities, but these results probably reflect the use of suboptimal CT and MR techniques. Recent evidence suggests that EUS is similar to CT in diagnosis and staging of pancreatic cancer. EUS requires special endoscopic skills and expertise, and it is less readily available worldwide. EUS-guided fine-needle aspiration (FNA) is safe and effective, especially for pancreatic head masses. EUS-guided FNA has sensitivity and specificity similar to that of CT-guided FNA cytology (FNAC). Limitations of TechniquesThe detection of a mass on imaging is nonspecific and 5-15% of pancreatic resections show benign pathology. Transabdominal US (TAUS) has a relatively poor sensitivity, and its results are not satisfactory for assessment in approximately 20% of patients because of a poor acoustic window due to bowel gas. MRI is sensitive in the detection and staging of pancreatic cancer with sensitivity and specificity similar to that of multisection CT. MRI involves expensive equipment and meticulous attention to the image technique. Other technical limitations are movement artifacts due to bowel peristalsis and breathing. Because the high sensitivity and specificity of MRI in detection and staging small tumors has not been achieved consistently and universally, debate continues about the superiority of MRI over CT. Multisection CT should be used first in the detection of pancreatic adenocarcinoma. When CT findings are negative, MRI or EUS should be applied for detection and for the assessment of resectability. Although conventional angiography is obsolete in primary staging, it is occasionally required to assess peripancreatic vessels before surgery. Modern multislice CT scanners are capable of excellent depiction of arterial and venous branches. The role of MR angiography (MRA) in the assessment of mesenteric vessels prior to surgery is not firmly established, though some encouraging study results are reported. DIFFERENTIALSSection 3 of 12
Pancreas, Islet Cell Tumors Pancreas, Mucinous Cystic Neoplasm Pancreas, Serous Cystadenoma Pancreatitis, Chronic RADIOGRAPHSection 4 of 12
FindingsPlain radiographs have no role in establishing a firm diagnosis of pancreatic carcinoma. Pancreatic calcifications may be seen concurrently in approximately 2% of patients who have chronic pancreatitis complicated by pancreatic carcinoma. Upper GI barium studies may reveal an extrinsic impression of the mass on the posteroinferior aspect of the antrum of the stomach. This is known as antral pad sign. The medial margin of the descending duodenum may be pulled medially at the level of the ampulla, forming a reversed-3 appearance. This is known as Frostberg 3 sign. Infiltration of the duodenal mucosa may cause a spiculated appearance with irregularity and thickening of the duodenal mucosa. The changes also may represent a desmoplastic response to malignant disease. A nodular mass with an ampullary carcinoma may be observed. Barium enema studies may demonstrate loss of normal haustral pattern from haustral padding along the transverse colon. The studies may show infiltration of the colon with an irregular or serrated contour to the bowel margin along the transverse colon, up to the level of splenic flexure. Tethering of colonic or small bowel margins resulting in asymmetry may occur from intraperitoneal seeding of pancreatic carcinoma. Degree of ConfidenceIn the presence of jaundice, barium studies have reasonably good specificity. The disease is usually advanced by the time the mass produces the characteristic signs on barium studies. False Positives/NegativesFalse-positive results may occur from a pseudocyst or other mass lesions producing similar appearances on the duodenal C-loop. Small masses may produce false-negative results. CT SCANSection 5 of 12
FindingsFeatures suggestive of underlying pancreatic cancer include the following: alterations in morphology of the gland with abnormalities of CT attenuation values, obliteration of peripancreatic fat, loss of sharp margins with surrounding structures, involvement of adjacent vessels and regional lymph nodes, pancreatic ductal dilatation, pancreatic atrophy, and obstruction of the common bile duct (CBD). Abnormal morphology of the gland, such as a change in size, shape, or attenuation values, may include focal or diffuse enlargement, a focal lobulated eccentric mass, or decreased attenuation of the mass, respectively. Focal enlargement A change in size is usually focal, and focal enlargement is seen in about 96% of patients with pancreatic adenocarcinoma. The size is an unreliable indicator of tumor, as a normally sized pancreatic head is consistent with a carcinoma of pancreas when atrophy of the body and tail is observed. This feature may be seen in pancreatic carcinoma in as many as 20% of patients. Focal enlargement also can occur in benign disease; thus, it is a nonspecific finding. Diffuse enlargement is less common and usually suggests pancreatitis. By the time the mass has grown to produce a focal enlargement, the mass has often progressed to an inoperable stage. Some small tumors may cause biliary ductal obstruction and appear early. A change in the shape of the gland in the absence of enlargement is a more important sign and may suggest underlying tumor. Demonstration of fatty interstices within the mass suggests that the focal lobulation is of normal pancreas. If the fatty interstices are absent and if the mass is completely solid, it is more likely to be abnormal, and a biopsy is recommended. The normal pancreas has an attenuation value of 30-50 HU. A central zone of decreased attenuation occurs in 83% of patients. The margins of the low-attenuating mass usually are poorly defined and correspond to a hypovascular scirrhous tumor. Pancreatic tumor also may undergo central necrosis to produce a low density, and the tumor then simulates a small pseudocyst. Needle biopsy is occasionally needed to differentiate necrotic tumor from pseudocyst as a result of focal pancreatitis. The pancreatic tumors are hypovascular and are best demonstrated with the intravenous administration of contrast material and by acquiring images across the mass in the parenchymal arterial phase. The mass is seen as a low-attenuating lesion in the brightly enhancing surrounding parenchyma. Dilatation Ductal dilatation occurs in 58% of patients. Among patients with ductal dilatation, 75% have dilation of both the pancreatic ducts and the biliary ducts. Pancreatic ductal dilatation proximal to the obstructing tumor is detected in approximately 88% of pancreatic head tumors and 60% of pancreatic body neoplasms. The duct size in pancreatic cancer is 5-10 mm, and the duct is either smooth or beaded. The pancreatic duct is dilated to more than 50% of the anteroposterior diameter of the gland in pancreatic cancer from atrophy of the gland. In chronic pancreatitis, duct dilatation is less than 50% of the anteroposterior (AP) diameter. Loss of normal peripancreatic fat-plane attenuation is suggestive of extension of tumor beyond the margins of the gland with invasion. The peripancreatic fat shows an increase in attenuation. Extension to involve peripancreatic fat and surrounding structures is observed on CT scans in 92% of patients. Metastasis Vascular encasement usually determines unresectability and is seen on CT as narrowing, displacement or obliteration of the vessel lumen by surrounding tumor. Collateral venous circulation may be observed from venous occlusion with contrast-enhanced vessels around the stomach and splenic hilum. Arterial encasement is usually well demonstrated by good-quality CT scans, and angiography is unnecessary. The arterial involvement, in descending order of frequency, is as follows: superior mesenteric, splenic, celiac, hepatic, gastroduodenal, and left renal. Spread to surrounding organs may involve the spleen, stomach, duodenum, splenic flexure of the colon, transverse mesocolon, porta hepatis, kidney, and spine. Local, posterior tumoral extension into the porta hepatis is seen in approximately 68% of patients. The presence of ascites indicates peritoneal metastatic disease with implants. Ascites is seen in 13% of patients with pancreatic cancer. The peritoneal deposits are poorly demonstrated by means of CT. Regional lymph-node metastasis has been reported to vary from 38-65%. Metastasis to liver is the most common in pancreatic cancer, occurring in approximately 17-55%. The CBD is displaced anteriorly and medially when the pancreatic mass causes distal ductal obstruction. Intrahepatic ductal dilatation and gall bladder dilatation can be demonstrated. Degree of ConfidenceAt present, CT is the most widely used and most sensitive test for an evaluation of the pancreas for pancreatic carcinoma. Dynamic CT has a detection rate of approximately 99%. Multisection CT should be the first-line study for detecting this tumor and for evaluating its resectability. False Positives/NegativesCysts or focal pancreatitis can occasionally cause problems in diagnosis, and it can produce false-positive and false-negative results. MRISection 6 of 12
FindingsThe role of MRI in the management of pancreatic adenocarcinoma has yet to be firmly established. Compared with other modalities, MRI appears to be more valuable for staging the extent and spread of pancreatic carcinoma than for tumor detection of lesions smaller than 2 cm. The ability of MRI to demonstrate pancreatic adenocarcinoma largely depends on the demonstration of deformity of the gland, as reflected in its size, shape, contour, and signal intensity characteristics. The criteria to suspect a mass are similar to those applied with CT, as discussed above. Rarely, nonenhanced MRI reveals a carcinoma of the pancreas before it deforms the gland. However, when such a feature is encountered, the dilemma to distinguish the focal abnormality from focal pancreatitis becomes challenging. An alteration in signal characteristics is less specific for tumor because the tissue relaxation times between pancreatic cancer, pancreatitis, and controls can overlap significantly. The mean T1 relaxation time of normal pancreas is 507 ms ±98, and the T1 relaxation time of pancreatic tumor is about 660 ms ±115. The T2 relaxation time of normal pancreas is 59 ms ±9, and the T2 relaxation time of pancreatic tumor is 67 ms ±29. The normal pancreas is of low signal intensity on T1-weighted images and of intermediate signal on T2-weighted images, with a variable amount of fat in the gland parenchyma. Newer techniques to obtain images using breath-hold techniques and advances in body coil technology and faster techniques have made it possible to acquire images with excellent spatial resolution. T1-weighted fat-suppressed spin-echo and single–breath-hold gradient-echo fast low-angle shot (FLASH) sequences with gadolinium enhancement are valuable for tumor detection. The mass is demonstrated as a low-intensity lesion within a homogeneously enhancing normal pancreatic gland. Intravenous Gd-enhanced FLASH images obtained 10 s after contrast enhancement has proven to be more sensitive in demonstrating tumor than other techniques. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble movingor straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape. Magnetic resonance cholangiopancreatography (MRCP) is as sensitive as ERCP and may prevent inappropriate explorations of the pancreatic and bile ducts in patients with suspected pancreatic carcinoma in whom interventional endoscopic therapy is unlikely. The sensitivity of MRCP in a study of 124 patients was 84% with a specificity of 97% for pancreatic cancer. The findings are complimentary to those of ERCP and percutaneous transhepatic cholangiography (PTC). Degree of ConfidenceIt has been difficult to prove consistent results using MRI in demonstrating the tumor and its resectability. The degree of confidence with MRI is less than that with CT at the moment because of the wide variability in MRI techniques and its limitations from motion artifacts. Recent studies have demonstrated results confirming greater reliability with MRI performed by using meticulous technique. ULTRASOUNDSection 7 of 12
FindingsThe lesion may have a variable appearance on US. It may be hypoechoic, isoechoic, or hyperechoic to the normal pancreas. Pancreatic ductal dilatation and biliary ductal dilatation are easily demonstrated in patients with a tumor in the head of pancreas that causes an obstruction. Lymphadenopathy, the relation of the tumor to peripancreatic vessels, and the tumor margins are demonstrated less reliably with US than with other modalities. The mass appears as an irregular hypoechoic mass that infiltrates a bright pancreatic parenchyma. Degree of ConfidenceThe degree of confidence may be improved by using EUS in the detection of tumors smaller than 2 cm. US equipment has improved considerably in recent years, and this is likely to have reflected on the sensitivity for detecting pancreatic masses. TAUS examination is still less sensitive than other modalities in the detection of pancreatic malignancy smaller than 2 cm. It has a sensitivity of 70% and a specificity of 95% for the diagnosis of pancreatic malignancy. The specificity of EUS for differentiating benign from malignant lesions using US appearance alone remains unsatisfactory. EUS has a high sensitivity and specificity for pancreatic cancer, with an overall staging accuracy higher than 80%. The possibility of performing EUS-guided FNA significantly improves both diagnostic and staging capability of EUS. EUS-guided FNA is safe with a morbidity of less than 2%. In a recent review of 63 patients, the assessment of tumor resectability with EUS was compared with an assessment with MRI. The sensitivity for EUS for resectability was 61% and that of MRI was 73%. When EUS and MRI were used together, the sensitivity was 89% for resectability. NUCLEAR MEDICINESection 8 of 12
FindingsThe detection of a pancreatic tumor and distinguishing its appearances from those of other focal pancreatic diseases has remained a challenging diagnostic problem. Positron emission tomography (PET) is based on functional changes in the pancreatic cancer cells caused by enhanced glucose utilization as in any other malignant tissue. With 2-[fluorine 18]-fluoro-2-deoxy-D-glucose (FDG), PET can be used to identify pancreatic cancer and differentiate it from chronic pancreatitis with a sensitivity of 85-98% and a specificity of 53-93%. PET maps the metabolic activity at a molecular level; therefore, the uptake of FDG by neoplastic tissue is also dependent on factors such as tissue oxygenation, regional blood flow, and a peritumoral inflammatory reaction. PET is also useful in staging and determination of resectability of the tumor at the time of initial diagnosis. PET also has been shown to be an effective tool in the follow-up care of patients with pancreatic cancer. In more than 50% of patients in one study, additional information using PET influences the therapeutic procedure. Degree of ConfidenceIn general, the sensitivity of PET is high in the detection of lesions more than a centimeter in diameter. Early detection because of increased metabolic activity in cancer usually precedes the structural changes detected with US, MRI, or CT. PET has shown some promise in the detection of tumors, with high sensitivity and specificity. PET is dependent on tumor stage. However, further clinical trials are required to demonstrate the limitations of PET in the assessment of early pancreatic cancer. False Positives/NegativesPET is not an absolute technique as it fails to demonstrate pancreatic adenocarcinoma smaller than 1 cm. False-positive results may occur when focal pancreatitis is associated with early pancreatic carcinoma. ANGIOGRAPHYSection 9 of 12
FindingsAngiography is an invasive procedure that demands considerable operator skill and high-quality radiographic technique. Selective arteriograms obtained with an injection of iodinated contrast through the celiac axis and superior mesenteric artery with some magnification techniques may be required to demonstrate detail. Pancreatic carcinoma is relatively avascular and associated with neovascularity in 50% of patients. Pancreatic malignancy usually demonstrates arterial encasement of peripancreatic vessels or, actually, of vessels within the pancreas. The vessels involved are the following, in descending order of frequency: superior mesenteric artery (33%), splenic artery (14%), celiac artery (11%), hepatic artery (11%), gastroduodenal artery (3%), and left renal artery (0.6%). When the disease is advanced, venous occlusions and venous encasement with collateral vessels may be observed. Superior mesenteric vein encasement by tumor is seen in 23%, and the splenic vein is encased by tumor in 15%, with portal vein infiltration in 4%. Complete occlusion of the splenic vein is seen in 34%, and complete occlusion of the superior mesenteric vein is seen in 10%. Pancreatic carcinoma can be distinguished from pancreatitis. The demonstration of hypervascularity with the typical beaded changes of alternating narrowing with dilatation of internal pancreatic vessels is a feature of pancreatitis. The mesenteric circulation has been evaluated by using MRA and compared with conventional angiography. Excellent agreement was seen between MRA and conventional angiography. Gd-enhanced MRA is useful in the evaluation of proximal mesenteric arteries and in the evaluation of portal hypertension. Conventional angiography is needed for the evaluation of intrahepatic arteries and branches of the superior mesenteric artery. Degree of ConfidencePancreatic carcinoma is a hypovascular lesion; therefore, angiography has rightly been replaced as the method of choice for evaluation of pancreatic parenchymal disease. Helical CT angiography shows useful information about the peripancreatic vessels in patients with pancreatic carcinoma. In a study of 84 patients, the negative predictive value of a resectable tumor was 96% for helical CT angiography and axial helical CT compared with 70% for helical CT alone. The addition of helical CT angiography improves the radiologist's ability to predict the resectability of pancreatic tumors. False Positives/NegativesAngiography has an accuracy of only 70% in making a specific diagnosis of pancreatic carcinoma. INTERVENTIONSection 10 of 12
Endoscopic retrograde cholangiopancreatography Pancreatography is abnormal in 95% of patients. ERCP has a sensitivity of 95% and a specificity of 85% for pancreatic malignancy. Most pancreatic carcinomas arise from the ductal epithelium and produce complete or partial ductal obstruction. The pancreatic duct may show significantly dilated ducts proximal to the point of obstruction with abrupt cutoff of contrast column. Incomplete filling can be distinguished from obstruction as the contrast column gradually tapers and fades away. Nonfilling of the duct because of technique is an important cause of false-positive findings. The pancreatic ducts between the obstruction and the papilla of Vater are usually normal. This important finding may help to distinguish pancreatic carcinoma from pancreatitis. The ducts from point of obstruction to papilla of Vater are usually abnormal in pancreatitis. Pancreas divisum, a congenital variation seen in approximately 10% of the population, is another cause of false-positive findings. Injection into the major papilla will opacify a short segment of duct in the head of pancreas. When the minor papilla is injected separately, the remainder of the larger part of the pancreatic ductal system opacifies. This is due to an embryologic failure of fusion of a portion of the head of pancreas with the rest of the gland. Involvement of both the pancreatic and CBD, termed double-duct sign, was originally described as being specific for carcinoma. It also may be seen in pancreatitis. Features that suggest a neoplasm are biductal lesions in close proximity less than 1 cm apart, abrupt stricture with irregular margins, and complete or high-grade obstruction of the CBD. The CBD may show a rat-tail or nipplelike occlusion. Widely separated strictures and smooth narrowing indicate benign disease. Pancreatography also may show acinar defects. An ultrathin pancreatoscope is used for diagnostic pancreatoscopy, which does not necessitate sphincterotomy. Intraductal tumor increasingly has been demonstrated by this technique. The use of noninvasive imaging such as MRCP has gained a considerable foothold in recent years in the preassessment of ductal morphology to diagnose pancreatic malignancy. MRCP is as sensitive as ERCP, and it may prevent inappropriate explorations of the pancreatic and bile ducts in patients with suspected pancreatic cancer in whom interventional endoscopic therapy is unlikely. In a study of 124 patients, the sensitivity of MRCP was 84% with a specificity of 97% for the diagnosis of pancreatic cancer. Biliary obstruction by malignant disease from pancreas resulting in jaundice will require biliary stenting. Controversy continues regarding the best route of drainage. When endoscopic stenting fails or is contraindicated, percutaneous biliary drainage is recommended. Percutaneous transhepatic biliary drainage (PTBD) When endoscopic biliary drainage is unsuccessful or is contraindicated, percutaneous transhepatic biliary drainage (PTBD) is recommended. The risk of complications is increased in comparison with that of the endoscopic technique. The 30-day mortality rate in the percutaneous group of patients is 33%, compared with 15% for the endoscopic group. The overall long-term survival is approximately equivalent whether drainage is performed endoscopically or percutaneously. PTBD poses an increased risk of hemobilia, intrahepatic hematoma, cholangitis, hemoperitoneum, biliary peritonitis, and pleuritis. Broad-spectrum antibiotic coverage is recommended. Cephalosporins are more potent than other drugs in prophylactic use. Infective cholangitis is a complication of PTBD in approximately 4% of patients. In an early review, researchers thought that the operative mortality and morbidity of patients undergoing pancreatic resection could be reduced with preoperative percutaneous biliary drainage. However, a randomized study failed to confirm this impression. In summary, intubation via an endoscopic route in patients with cardiovascular, renal, or other metabolic conditions allows time to prepare them for potentially curative surgery. For other patients, biliary drainage prior to planned surgery offers no significant advantage. Therapeutic biliary stent placement Results of prospective randomized studies suggest that biliary stenting may replace surgical intervention in most patients. In patients who have advanced disease and who are candidates for neoadjuvant therapy, stent placement may be preferable to surgical intervention. Furthermore, no evidence suggests that laparoscopic cholecystojejunostomy is better than endoscopic or percutaneous biliary drainage. Pancreatic cancer screening Evidence is inconclusive that early detection in subgroups at risk for pancreatic cancer would improve survival. No reliable screening tests are available for detecting early pancreatic cancer in asymptomatic patients. Imaging techniques are not suitable as screening tests because of many factors, including cost and/or their invasive nature. Tumor markers are nonspecific. Screening for pancreatic cancer is not recommended at this time. Pancreatic biopsy For a final diagnosis, histologic or cytologic confirmation is needed. The reported sensitivity and diagnostic accuracy are high for both histologic and cytologic examinations. Specificity is near to 100% in most published series. These studies are from centers of excellence. However, in practice, obtaining a diagnosis by means of percutaneous biopsy can be problematic, and in some patients malignancy is confirmed on follow-up images, which demonstrate an increase in the size of a lesion or by hepatic metastases. Percutaneous FNA biopsy does pose a small but real risk of tumor implantation along the biopsy track of the needle. It has a clear advantage in patients with advanced disease in whom the diagnosis is to be established without subjecting the patient to surgery. A Tru-cut biopsy using 18-gauge needle can be safely and effectively performed under guidance. Microscopic confirmation is required in all patients in whom chemotherapy, radiation therapy, or both are planned. For attempted radical surgery, biopsy is not mandatory if the clinical suspicion of cancer is high and the surgical team has documented low postoperative morbidity and mortality rates. FNAC does not allow sufficient yield to characterize the subtype of the pancreatic carcinoma. The morbidity of pancreatic fistula from FNAC can be reduced by using a transduodenal approach. The sensitivity of EUS-guided FNA is 75-97%, similar to that of CT-guided FNA. Pancreatic mass FNA is highly sensitive and specific (94-100%) for lesions smaller than 3 cm in diameter. Similar high specificity is found with EUS-guided FNA of lymph nodes. An FNA specimen is almost always adequate. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Pancreas, Adenocarcinoma excerpt Article Last Updated: Apr 13, 2007 | ||||||||||||||
