Solitary Pancreatic Lesions Found on Imaging

During an ultrasound, a computed tomography (CT) or a magnetic resonance (MR) scan, a single cyst, nodule or mass may sometimes be found by chance in the pancreas.

This naturally causes anxiety in patients. But there is an important point:

Not every lesion seen in the pancreas is pancreatic cancer.

Some pancreatic lesions are entirely benign. Some need only follow-up, while others may have the potential to turn into cancer over time. A proportion may be malignant at the time of diagnosis.

For this reason the aim is to identify the risky lesions in good time while avoiding unnecessary operations.

Is the pancreatic lesion cystic or solid?

This is one of the first important distinctions when a lesion found in the pancreas is assessed.

A cystic lesion is filled with fluid or fluid-like content.

A solid lesion consists mostly of solid tissue.

This distinction matters, because the possible conditions and the course to follow differ from one another.

Which cystic lesions may be seen in the pancreas?

The cystic lesions met with most often include:

• IPMN (intraductal papillary mucinous neoplasm),
• Mucinous cystic neoplasm (MCN),
• Serous cystic neoplasm (SCN),
• Pseudocyst.

Other, rarer cystic lesions may also be seen.

What is an IPMN?

An IPMN is a cystic lesion arising from the pancreatic ducts, which can produce a thick fluid called mucin.

IPMNs can be considered in two main groups: main-duct IPMN and side-branch IPMN.

Side-branch IPMNs in particular are now found by chance quite often during MR scans.

Not every IPMN is cancer.

But some IPMNs have the potential over time to show high-grade cellular changes or to turn into pancreatic cancer.

For this reason what is assessed is the IPMN’s:

• Size,
• The width of the main pancreatic duct,
• Whether there is a nodule within it,
• Whether it has grown over time,
• Whether it is causing symptoms in the patient.

A substantial proportion of low-risk IPMNs can be followed with regular imaging without an operation.

What is a mucinous cystic neoplasm (MCN)?

An MCN is a cystic lesion seen mostly in women and in the body or the tail of the pancreas.

Unlike an IPMN, it generally has no connection with the main pancreatic duct.

MCN matters because it can carry the potential to become cancer.

The size of the lesion, its imaging features, whether there is a nodule or a solid part within it, and the patient’s circumstances are all taken into account in the decision on treatment.

Surgical treatment may be advised in some MCNs.

What is a serous cystic neoplasm?

A serous cystic neoplasm is mostly a benign pancreatic cyst.

Treatment is mostly not needed in patients with typical imaging features and no symptoms.

Treatment may come into consideration if it grows very large or causes complaints by pressing on neighbouring organs.

It is extremely rare for a serous cystic neoplasm to become malignant.

What is a pancreatic pseudocyst?

A pseudocyst is not a true tumour.

It generally develops after:

• Acute pancreatitis,
• Chronic pancreatitis,
• Injury to the pancreas.

For this reason it is very important to know whether the patient has had pancreatitis before.

Not every pseudocyst has to be drained. Its size, the symptoms, the development of infection and other complications determine the decision on treatment.

What is considered if a solid lesion is found in the pancreas?

Solid pancreatic lesions need more careful assessment.

The possibilities may include:

• Pancreatic ductal adenocarcinoma,
• Pancreatic neuroendocrine tumour (NET),
• Solid pseudopapillary neoplasm,
• Focal pancreatitis,
• Autoimmune pancreatitis,
• Other, rarer tumours.

It is not right to think solid lesion = cancer.

But a newly found solid pancreatic mass in particular needs detailed assessment without delay.

Pancreatic adenocarcinoma

The commonest malignant tumour of the pancreas is pancreatic ductal adenocarcinoma.

Tumours in the head of the pancreas in particular may present with:

• Jaundice,
• Darkening of the urine,
• Paling of the colour of the stool,
• Itching.

Alongside these, findings such as:

• Unexplained weight loss,
• Loss of appetite,
• Upper abdominal pain or pain going through to the back,
• Newly begun diabetes, or diabetes whose control suddenly deteriorates

may be seen.

But small pancreatic lesions can sometimes be found on imaging with no symptoms at all.

What is a pancreatic neuroendocrine tumour (NET)?

These are tumours developing from the hormone-producing cells of the pancreas.

Some produce hormone and some do not.

The behaviour of these tumours varies considerably. Some grow slowly over years while others can be more aggressive.

For this reason:

a pancreatic NET is not necessarily a pancreatic adenocarcinoma.

Treatment is decided according to the size of the tumour, its position, whether it produces hormone, its grade and its extent.

What is a solid pseudopapillary neoplasm?

This is a rare tumour of the pancreas.

It is seen particularly in young women and mostly has a low-grade malignant potential.

In patients in whom it can be removed completely by surgery, the results are generally quite good.

What is done first when a lesion is found in the pancreas?

The first imaging method may not always be enough to characterise the lesion fully.

Where a lesion is seen in the pancreas on an ultrasound done for another reason, for instance, more detailed investigation may be needed.

Generally contrast CT with a pancreas protocol and/or pancreatic MR with MRCP are used.

MRCP is particularly useful for assessing the pancreatic ducts and for showing the connection of a cystic lesion with the pancreatic duct.

Why does EUS matter?

Endoscopic ultrasound (EUS) is an extremely valuable method in assessing pancreatic lesions.

A thin endoscope with an ultrasound device at its tip is passed into the stomach and duodenum. Because the pancreas lies immediately alongside these organs, it can be imaged from very close by and at high resolution.

EUS can assess in detail:

• The size of the lesion,
• Whether it is cystic or solid,
• Any nodules within it,
• The pancreatic ducts,
• The surrounding lymph nodes.

Can a biopsy be taken with EUS?

Yes.

Where necessary, a sample can be taken from the lesion with a fine needle during EUS.

This is called EUS-guided tissue sampling.

In solid lesions a tissue sample can be taken for pathological examination.

In cystic lesions, cyst fluid can be taken where needed for tests such as:

• Cytology,
• Glucose,
• CEA,
• Molecular investigations.

But not every pancreatic cyst needs needle sampling.

EUS and sampling are preferred where the result would change the patient’s follow-up or treatment plan.

Which features call for more attention?

Certain imaging and clinical features of pancreatic cysts may call for more detailed assessment.

Findings such as:

• A solid nodule within the cyst,
• Marked widening of the main pancreatic duct,
• Growth of the cyst over time,
• A thickened or irregular cyst wall,
• Pancreatitis that may be related to the cyst,
• Jaundice,
• A suspicious solid part

matter here.

The presence of one of these does not necessarily mean cancer, but it does call for further assessment.

Does a raised CA 19-9 mean cancer?

No.

CA 19-9 is a tumour marker that can be used in assessing diseases of the pancreas.

But:

a raised CA 19-9 = pancreatic cancer

does not hold.

It can also be raised in obstruction of the bile duct and in certain benign conditions.

Equally, a normal CA 19-9 value does not definitely exclude pancreatic cancer.

For this reason CA 19-9 is not used on its own as a diagnostic test.

Does every pancreatic cyst have to be operated on?

No.

This is one of the things patients most often worry about.

Today a substantial proportion of pancreatic cysts are followed up rather than operated on.

This is because operations on the pancreas are major surgical procedures and unnecessary surgery has to be avoided.

The decision is made by assessing together:

the kind of cyst + its size + its rate of growth + the presence of a nodule + the pancreatic duct + the patient’s age and general state of health.

How long does follow-up last?

A single follow-up programme is not suitable for all pancreatic cysts.

The intervals of follow-up are decided according to:

• The kind of cyst,
• Its size,
• Its imaging features,
• Its change over time,
• The patient’s age,
• Their fitness for surgery.

Some small, low-risk cysts can be followed at long intervals, while lesions with risky features may need closer follow-up or surgical assessment.

Why do older images matter?

When a lesion is found in the pancreas, CT or MR images taken in earlier years are extremely valuable.

For instance:

• a cyst that has stayed the same size for 5 years, and
• a lesion that has grown markedly within 6 months

are not assessed in the same way.

For this reason older imaging reports and, where possible, the images themselves should be shown to the doctor.

When is quicker assessment needed?

In a person with a lesion found in the pancreas, assessment should not be delayed particularly where there is:

• Jaundice,
• Unexplained weight loss,
• Newly begun, constant abdominal or back pain,
• Recurrent pancreatitis,
• Newly developed or unexplainably worsening diabetes,
• Loss of appetite,
• A solid component or a nodule on imaging,
• Marked widening of the main pancreatic duct,
• Rapid growth of the lesion.

The important message

Not every lesion found in the pancreas on imaging is cancer.

A substantial proportion of pancreatic lesions found by chance are cystic, and most of these do not require an immediate operation.

But pancreatic cysts are not all the same.

Serous cystic neoplasms are mostly benign. IPMNs and mucinous cystic neoplasms can carry, to varying degrees, the potential to become cancer. Solid pancreatic lesions need quicker and more detailed assessment.

Pancreas-protocol CT, MR/MRCP and, where needed, EUS are complementary methods in making the diagnosis. During EUS, a tissue or cyst fluid sample can be taken in the patients who need it.

The aim is not to operate on every lesion but to follow the low-risk ones safely, and to identify the high-risk or malignant ones in good time.

This content has been prepared for general information. Assessment of lesions found in the pancreas should be made by considering the imaging features, the patient’s age, their symptoms, their family history and other risk factors together.