A Cyst Was Found in the Pancreas: What Does It Mean?

Finding a “cyst”, a “cystic lesion” or a “cystic structure” in the pancreas during an ultrasound, CT, MRI or MRCP can naturally cause worry.

But the first thing to know is this: finding a cyst in the pancreas does not mean you have pancreatic cancer.

A large proportion of pancreatic cysts are found by chance (incidentally) during imaging done for some other reason. Some of them are entirely harmless. Others need watching to see whether they change over time. In a smaller proportion there can be a potential to become cancer.

So the real question is not “is there a cyst?” but “what type is this cyst and what are its risk features?”

What is a pancreatic cyst?

A pancreatic cyst is a fluid-containing structure within, or associated with, the pancreas.

But not all pancreatic cysts are the same. What matters in the assessment is the cyst’s:

• Size
• Wall structure
• Whether it contains a nodule
• Relationship with the pancreatic duct
• The diameter of the main pancreatic duct
• Whether it grows over time

What types of pancreatic cyst are there?

Cystic lesions seen in the pancreas come in different types.

Serous cystic neoplasm

Mostly benign in character. Some show a characteristic appearance made up of many small cysts. Not every serous cyst needs treating.

Mucinous cystic neoplasm (MCN)

A mucin-producing cystic lesion of the pancreas. It is seen more often in women and frequently in the body or tail of the pancreas.

Because some MCNs have the potential to develop malignant change over time, assessment and, where needed, surgical treatment may be considered depending on the cyst’s features.

What is IPMN?

IPMN (intraductal papillary mucinous neoplasm) is a cystic lesion arising from the pancreatic ducts that can produce mucin. It is seen mainly as:

• Side-branch IPMN
• Main-duct IPMN

Side-branch IPMNs are quite often found incidentally on MRI and MRCP today.

IPMN is not pancreatic cancer. But because some IPMNs carry a risk of developing advanced cellular change or cancer over time, follow-up or treatment is needed according to their risk features.

What is a pancreatic pseudocyst?

A pseudocyst is not a true cystic tumour. It generally develops after:

• Acute pancreatitis
• Chronic pancreatitis
• Injury to the pancreas

It can contain pancreatic fluid.

This is why whether the patient has had pancreatitis before matters a great deal in assessing a cystic structure found in the pancreas.

Not every pancreatic cyst should be called a “pseudocyst”. In someone with no history of pancreatitis in particular, cystic neoplasms should also be considered.

Is a pancreatic cyst cancer?

Mostly not.

But pancreatic cysts are not a single group of conditions. Some are almost entirely harmless, while some cystic neoplasms can carry a potential to become cancer.

So it is right neither to say “a pancreatic cyst = cancer” nor to say “a pancreatic cyst does not matter”.

Does the size of the cyst matter?

Yes, but it is not enough on its own.

Large cysts may in some situations need more detailed assessment. But whether a cyst is benign or malignant cannot be told from its diameter alone. A suspicious wall nodule in a small cyst, for instance, can matter more than its size.

So the size and the structure of the cyst are assessed together.

Which features of the cyst matter?

In assessing a pancreatic cyst the following features are noted in particular:

• The diameter of the cyst
• Its relationship with the main pancreatic duct
• The width of the main pancreatic duct
• Whether the cyst contains a solid component
• Whether there is a wall nodule
• Thickening of the wall
• Enhancement characteristics
• A sudden change in duct calibre
• Atrophy of the pancreas
• Growth over time
• Whether the patient develops jaundice or pancreatitis

The presence of some of these may call for more detailed assessment.

What does “mural nodule” mean?

A mural nodule is a small projection of tissue seen in the wall of the cyst.

Not every mural nodule means cancer. But enhancing true mural nodules in particular can matter in the risk assessment of some pancreatic cysts. More detailed examination by MRI/MRCP or EUS may therefore be needed.

Does it matter if the pancreatic duct is wide?

Yes.

The diameter of the main pancreatic duct matters particularly in assessing IPMN. Marked widening of the main pancreatic duct can suggest main-duct IPMN or another blockage of the duct.

So if a report says “a pancreatic cyst + a wide main pancreatic duct”, the cyst’s diameter alone is not what is looked at.

Why does jaundice matter?

Some cystic lesions in the head of the pancreas can affect the bile duct. In someone with a pancreatic cyst who develops obstructive jaundice in particular, this is a situation that needs assessing more carefully.

Does a pancreatic cyst cause pain?

Most small pancreatic cysts cause no symptoms at all. Some people may have:

• Upper abdominal pain
• Pain spreading to the back
• Nausea
• Early fullness

But these symptoms are not specific to a pancreatic cyst. In everyone with abdominal pain who is found to have a pancreatic cyst, the cyst may not be the cause of the pain.

Can it cause pancreatitis?

Some pancreatic cysts can. In some IPMNs related to the pancreatic duct in particular, mucin can affect the flow in the duct and lead to an attack of acute pancreatitis.

In a patient with recurring pancreatitis of unexplained cause, the pancreatic ducts and any cystic lesions may need assessing.

Why do MRI/MRCP matter for a pancreatic cyst?

MRI, and MRCP in particular, are very useful in assessing pancreatic cysts. MRCP can show:

• The cyst’s relationship with the pancreatic duct
• The main pancreatic duct
• The side branches
• The number of cysts
• Some features of the internal structure

Because it involves no ionising radiation, it also offers an advantage for some patients who need long-term follow-up.

When might EUS be needed?

Endoscopic ultrasound (EUS) can image a pancreatic cyst in considerable detail. EUS may be considered particularly where:

• The structure of the cyst cannot be fully understood
• There is a suspicious wall nodule
• A solid component is suspected
• The main pancreatic duct is wide
• The cyst has risky features

Not every pancreatic cyst needs an EUS.

Is fluid taken from the cyst?

In some selected patients a sample of the cyst fluid can be taken with a fine needle during EUS. This is called EUS-guided cyst aspiration or sampling.

Depending on the clinical situation, the fluid obtained may be examined for:

• Cytology
• CEA
• Glucose
• Amylase
• Molecular analyses

But not every pancreatic cyst needs fluid taken from it. Sampling is chosen where the result will change how the patient is managed.

Does CA 19-9 matter?

The serum CA 19-9 level can help in assessing some pancreatic cysts.

But a raised CA 19-9 does not on its own mean pancreatic cancer. It can rise in harmless conditions such as a blocked bile duct, cholangitis and pancreatitis. Equally, a normal CA 19-9 does not definitively rule malignant disease out.

Is every pancreatic cyst operated on?

Certainly not.

Pancreatic surgery is a major undertaking and should be carried out only in patients who need it. The decision to treat is made by weighing the type of cyst, its size, its risk features, the patient’s age, their other conditions, the surgical risk and the expected benefit.

Some cysts are simply followed. Some need EUS. In others surgical treatment may be more appropriate.

How often is a pancreatic cyst followed up?

There is no single follow-up interval for every cyst. The interval is determined by:

• The type of cyst
• Its size
• Its risk features
• Its change since previous images
• The patient’s age
• Their general health

Some cysts are followed at shorter intervals, while for small low-risk cysts the intervals can be longer.

Does growth of the cyst matter?

Yes.

Marked growth of the cyst compared with previous MRI or CT scans matters in the assessment. This is why keeping your old imaging is very valuable.

A small cyst that has stayed the same size for years, for instance, is not assessed in the same way as one that has grown markedly in a short time.

Which features call for more careful assessment?

More detailed assessment may be needed where a pancreatic cyst shows:

• A solid component within the cyst
• An enhancing mural nodule
• Marked widening of the main pancreatic duct
• Obstructive jaundice related to the cyst
• Marked growth of the cyst
• A sudden change in duct calibre with distal pancreatic atrophy
• Recurring or cyst-related pancreatitis
• Additional findings such as a raised serum CA 19-9

The presence of one of these findings is not on its own a diagnosis of cancer.

Does age matter?

Yes. Pancreatic cysts are found more often as age advances.

In deciding on follow-up or treatment, not only the cyst’s features are considered but also the patient’s:

• Age
• General health
• Other conditions
• Fitness for surgery
• Life expectancy

So a cyst of the same size may not be managed the same way in two different patients.

Why should you keep your old MRI and CT scans?

With pancreatic cysts, change over time is very valuable. Being able to compare with old images helps the radiologist understand:

• Whether the cyst has grown
• Whether a new nodule has formed
• Whether the pancreatic duct has changed

Keep not only the report but, where possible, the images themselves.

When should assessment not be delayed?

What should you do if a pancreatic cyst is found?

1. Do not panic. Not all pancreatic cysts are cancer.
2. An attempt is made to determine the type of cyst. Simply saying “there is a cyst” is not enough.
3. Its size and structure are looked at. A wall nodule or a solid component matters particularly.
4. The pancreatic duct is assessed. Its width and its relationship with the cyst are investigated.
5. It is compared with old images. Whether there has been growth matters.
6. MRI/MRCP or EUS is done where needed.
7. Not every cyst is biopsied and not every cyst is operated on.
8. If follow-up is needed, it should not be neglected.

Remember

• A pancreatic cyst Is not on its own pancreatic cancer.
• IPMN Is not cancer; but some types can carry a potential to become cancer.
• A pseudocyst Is usually related to pancreatitis and is not a cystic tumour.
• MRI/MRCP Is very useful in assessing the cyst’s relationship with the pancreatic ducts.
• EUS Is used for the detailed assessment of selected cysts.
• Not every pancreatic cyst Needs an operation.
• Follow-up Is decided individually according to the cyst’s type, size and risk features.

The most important message

Finding a cyst in the pancreas is not on its own a diagnosis of cancer.

What really matters is what type the cyst is, its size, its relationship with the pancreatic duct, whether it contains a mural nodule or a solid component, and whether it has changed over time.