PANCREATIC CARCINOMA CLINICAL RADIOLOGY
Category: Diagnostic Radiology
Abstract : pancreatic carcinoma clinical features and management Carcinoma of the
pancreas is a major cause of cancer-related death. It carries a very poor
prognosis with less than 5% 5 year survival,10 related to its late presentation.
The presenting symptoms depend on the size of the lesion, its position within
the pancreas and the extent of metastatic deposits. Most pancreatic carcinomas
(60%
pancreatic carcinoma clinical features and management
Carcinoma of the
pancreas is a major cause of cancer-related death. It carries a very poor
prognosis with less than 5% 5 year survival,10 related to its late presentation.
The presenting symptoms depend on the size of the lesion, its position within
the pancreas and the extent of metastatic deposits.
Most pancreatic carcinomas
(60%) are found in the head of the pancreas, and patients present with the
associated symptoms of jaundice due to obstruction of the common bile duct.
Carcinomas located in the body or tail of pancreas do not cause obstructive
jaundice. The majority (80%) of pancreatic cancers are ductal adenocarcinomas,
most of which are located in the head of pancreas. The rest comprise a mixed bag
of less common neoplasms and endocrine tumours.
Endocrine tumours, which
originate in the islet cells of the pancreas, tend to be either insulinomas
(generally benign) or gastrinomas (malignant). These present with hormonal
abnormalities while the tumour is still small and are more amenable to detection
by intraoperative ultrasound than by conventional
sonography.
Mucin-secreting tumours , which appear predominantly cystic
on ultrasound, tend to be located in the body or tail of pancreas and follow a
much less aggressive course than adenocarcinomas, metastasizing late. These
tumours, though comparatively rare, have a much higher curative rate with
surgery. Metastatic deposits from primary pancreatic adenocarcinoma occur early
in the course of the disease, and 80% of patients already have nodal disease or
distant metastases in the lungs, liver or bone by the time the diagnosis is
made, which accounts for the poor prognosis.
Surgical removal of the
carcinoma by partial pancreaticoduodenectomy, the Whipples procedure, is
potentially curative but only 20% of patients have a tumour which is potentially
resectable, and the 5-year survival rate following resection is less than 5%.13
Over 70% of patients die from hepatic metastases within 3 years postoperatively.
Differential diagnoses of pancreatic masses must always be considered ; focal
lesions in the pancreas may represent inflammatory rather than malignant masses.
An ultrasound-guided biopsy is sometimes useful in establishing the presence of
adenocarcinoma if the biopsy is positive, but the sensitivity of this procedure
is relatively low. The value of a negative biopsy is dubious because of the
inflammatory element surrounding many carcinomas.
Endosonography-guided
biopsy, however, has high sensitivity and specificity for diagnosing pancreatic
cancer, and is also useful in patients with a previous negative biopsy in whom
malignancy is suspected. ERCP may also be used to insert a palliative stent in
the common bile duct, to relieve biliary obstruction. The detection of a
pancreatic carcinoma by ultrasound is usually followed by a CT scan for staging
purposes as this will demonstrate invasion of peripancreatic fat, vascular
involvement and lymphadenopathy.
Ultrasound appearances of pancreatic
carcinoma
The adenocarcinoma, which comprises 80% of pancreatic neoplasms, is
a solid tumour, usually hypoechoic or of mixed echogenicity, with an irregular
border. Because the mass is most frequently located in the head of the pancreas,
which lies behind the duodenum, it may be difficult to identify at first.
Endocrine tumours, which arise from the islet cells in the pancreas, include
insulinomas, which are benign, and gastrinomas, which are more often malignant.
They are usually hypoechoic, welldefined and exhibit a mass effect, often with a
distally dilated main pancreatic duct. They are generally smaller at
presentation than adenocarcinomas, and tend to arise in the body or tail of
pancreas. Up to 40% of these tumours go undetected by both transabdominal
ultrasound and CT, with endoscopic ultrasound and laparoscopic ultrasound having
the highest detection rates for insulinomas. Gastrinomas tend to be multiple and
may also be extrapancreatic.
A small proportion of pancreatic cancers
contain an obvious fluid content. Cystadenocarcinomas, which produce mucin, are
similar in acoustic appearance to a pseudocyst, but unlike a pseudocyst, a
mucinous neoplasm is not associated with a history of pancreatitis. It is also
possible within a lesion to see areas of haemorrhage or necrosis which look
complex or fluid-filled. Calcification is also seen occasionally within
pancreatic carcinomas. The adenocarcinoma is vascular and highvelocity arterial
flow may be identified within it in many cases.
The pancreatic duct
distal to the mass may be dilated. It may, in fact, be so dilated that it can be
initially mistaken for the splenic vein. The walls of the duct, however, are
usually more irregular than the smooth, continuous walls of the splenic vein.
Colour Doppler is useful in confirming the lack of flow in the duct and in
identifying the vein behind it.
Secondary ultrasound findings in
pancreatic adenocarcinoma
The most obvious secondary feature of carcinoma of
the head of pancreas is the dilated biliary system. In a recent series of 62
pancreatic cancers, biliary dilatation occurred in 69%, pancreatic duct
dilatation in 37% and the double duct sign (pancreatic and biliary duct
dilatation) in 34% of patients. Although the gallbladder is frequently dilated
with no visible stones, this is not always the case; incidental gallstones may
be present, causing chronic inflammation which prevents the gallbladder from
dilating. For this reason it is imperative that the common duct is carefully
traced down to the head of pancreas to identify the cause of obstruction. A
thorough search for lymphadenopathy and liver metastases should always be made.
CT is usually the method of choice for staging purposes. If the mass is large,
it is not possible to differentiate whether it arises from the ampulla of Vater
or the head of pancreas. This differentiation, however, is usually academic at
this stage.
Colour Doppler can demonstrate considerable vascularity
within the mass and is also important in identifying vascular invasion of the
coeliac axis, superior mesenteric artery, hepatic, splenic and/or gastroduodenal
arteries and of the portal and splenic veins, a factor which is particularly
important in assessing the suitability of the tumour for curative resection. The
recognition of involvement of peripancreatic vessels by carcinoma with colour
Doppler, together with the ultrasound assessment of compression or encasement of
these vessels, has been found to be highly sensitive and specific (79% and 89%)
for diagnosing unresectability, thus the need for further investigative
procedures such as CT may be avoided, particularly in cases of large tumours.
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