Benign and malignant neoplastic lesions of the pancreas produce a
variety of morphologic changes in the pancreas that can be detected by
different imaging modalities. Pancreatic cancers account for 2% of
all cancers, and comprise 5% of all cancer deaths. The survival
rate for pancreatic cancers remains low at 4%; it is up from 3% in
1974-76. The list below shows the various types of pancreatic
neoplasms.
|
|
Pancreatic Neoplasms
- Ductal Adenocarcinoma
- Intraductal papillary mucinous tumor
- Nonductal neoplasms
- Cystic neoplasms
- Mucinous macrocystic neoplasm
- Serous microcystic neoplasm
- Endocrine tumors
- Insulinoma
- Gastrinoma
- Glucagonoma
- VIPoma
- Somatostatinomas
- Solid & papillary epithelial neoplasm
- Metastasis
|
|
Initial symptoms of pancreatic adenocarcinoma are frequently
non-specific. Abdominal pain, jaundice, and weight loss are common.
Most (60-70%) of these tumors are in the head of the pancreas, and 70%
of these patients have obstructive jaundice as a result of common bile
duct obstruction. Patients with more advanced cancers experience weight loss
secondary to anorexia and pancreatic insufficiency. Lab studies reveal
elevated serum bilirubin, transaminases, alkaline phosphatase. Levels
of pancreatic enzymes (amylase, lipase, and elastase I) are elevated in
only 30% of patients due to main pancreatic duct obstruction. Tumor
markers (CA19-9, DUPAN 2, Span 1, CEA) are reliable indicators of
advanced pancreatic carcinomas, but are rarely useful in diagnosis of
early stage tumors.
Tumors in the head of the pancreas are often detected earlier (at a
smaller size), because they quickly invade vital structures to cause
symptoms. Tumors of the body and tail are often larger at the time of
presentation. Carcinoma of the ampulla has the best prognosis, because
these lesions are detected at a smaller size/cause symptoms of
presentation earlier. In the United States, only 1-2% of patients with
pancreatic carcinoma live 5 years beyond the time of diagnosis, making
early diagnosis critical.
|
Ultrasound (US):
On US, pancreatic
adenocarcinomas appears as a hypoechoic mass, with poorly demarcated
borders, that enlarges the pancreas and deforms its contour. Carcinomas
as small as 5 mm can be visualized on US. US is also sensitive in
demonstrating pancreatic and biliary duct dilatation secondary to tumor
obstruction. In cases of small tumors, ductal dilatation may be the only sonographic evidence of disease. Extraglandular extension (into
vascular structures) is also a common feature of advance tumors; color
doppler is particularly useful in demonstrating involvement of the major
vessels. Hepatic and lymph node metastases are easily visualized,
although peritoneal metastases are more difficult to diagnose by US.
Focal pancreatitis may be indistinguishable, unless calcifications are
present (which are rare in adenocarcinomas).
Endoscopic US (EUS) can provide more sensitive imaging in the
diagnosis and staging of adenocarcinoma. EUS is indicated in patients with small
masses on US or CT, or patients with suspected adenocarcinoma, but
negative US and CT. With EUS, the body and tail of the pancreas, the
splenic vein, and left kidney are visualized from the stomach; the head
of the pancreas, pancreatic duct system, portal vein, and common bile
duct, are all visualized from the duodenum. Compared to other
modalities (US, CT, ERCP, and angiography), EUS is reported to be the
most sensitive for the visualization of pancreatic adenocarcinoma. |
|
|
Computed
Tomography (CT):
Intravenous contrast-enhanced helical CT is the radiologic modality of choice for
diagnosing and staging pancreatic adenocarcinomas. Oral contrast is also used to delineate the
borders of the small bowel. Tumors as small as 2 cm may be visualized
with helical CT. The tumors appear as a hypoattenuating mass on
contrast-enhanced CT (since they are hypovascular). The tumor margins
are poorly defined, and calcification is rare. Secondary CT findings
suggestive of adenocarcinoma include atrophy of the distal gland, and
dilatation of the proximal pancreatic duct and bile duct. Differentiation
of dilated duct between chronic pancreatitis and carcinoma may be
difficult unless other findings of pancreatitis are present
(calcifications, pseudocysts).
Advanced adenocarcinomas frequently invade peripancreatic vessels
and adjacent organs (stomach, duodenum, colon, spleen, left kidney,
adrenal gland). CT can demonstrate the encasement these vessels, and
show the perivascular adventitial changes associated with tumor
infiltration (thickening of caliber of the vessel). Liver metastases
are also visualized as hypoattenuating masses, while lymph node
metastases present as nodal enlargement. |
|
Adenocarcinoma
Findings on CT |
 |
-Focal
hypoattenuating mass (red arrow)
-Atrophy of the gland distal to the mass
-Change in shape of pancreas, even in absence of mass |
 |
-Bile duct dilation (red arrow)
-Loss of sharp margins w/ surrounding structures
-Fat plane obliteration/invasion |
|
Endoscopic Retrograde Cholangiopancreatography (ERCP):
ERCP is highly accurate in the diagnosis of pancreatic
adenocarcinoma; ERCP can demonstrate very small lesions that arise from
the duct epithelium. Although some of the changes in ERCP are
nonspecific for carcinoma, they direct further investigation.
Abnormalities of the pancreatic ductal system include obstruction, duct
dilation, and extravasation of contrast into the tumor. The tables
below highlights some common ductal findings on ERCP.
|
|
|
|
|
|
ERCP Findings in
Adenocarcinoma |
 |
Left: proximal stenosis with
prestenotic dilation |
 |
 |
| Above: Double
duct sign: stenosis of CBD and main pancreatic duct |
Above: Common
bile duct obstruction presenting with painless jaundice |
|
|
Magnetic Resonance Cholangiopancreatography (MRCP):
MRCP may also be of assistance in the diagnoses of pancreatic
adenocarcinoma. MRCP can depict strictures and dilation of the main
pancreatic duct. In some institutions, MRCP has replaced diagnostic
ERCP in the diagnosis of adenocarcinoma.
|
|
Magnetic Resonance Imaging (MRI):
Ductal adenocarcinoma may be evalauated with MRI using the same
general criteria used for other imaging modalities. Recent studies have
shown MRI techniques to be equal or superior to those of CT in depicting
tumor and peripancreatic extension. T1 weighted MRI images are required
for the diagnosis of pancreatic adenocarcinoma; the tumors appear as
lesions of low signal intensity. (On T2 weighted images, tumors and
normal parenchyma show little or no variation in intensity.)
Differentiation between pancreatitis and pancreatic carcinoma cannot be
made using signal intensity findings on T1- and T2-weighted images.
|
|
|
