Pancreatic Cysts

What is a pancreatic cyst?

Pancreatic cysts are structures that develop within or on the pancreas and mostly contain fluid.

Because ultrasound, computed tomography (CT) and magnetic resonance (MR) scans in particular are now done so often, pancreatic cysts are found more frequently than in the past. A substantial proportion of them are found by chance during imaging done for another reason, and cause no complaint at all.

Seeing a cyst in the pancreas does not mean having pancreatic cancer.

There are different kinds of pancreatic cyst. The potential of some to turn into cancer is so low as to be negligible, while others may carry a risk of becoming cancer over time. So what matters is not only the question “is there a cyst?” but the question “what kind of cyst is this, and does it have risky features?”

Are pancreatic cysts common?

Yes. Small cysts found by chance in the pancreas become more common as age advances.

With the spread of sensitive imaging methods such as MR, even cysts of a few millimetres can be noticed.

For this reason it is not unusual today for a small pancreatic cyst to appear on the MR report of a person with no complaints at all.

Is every pancreatic cyst the same?

No.

Pancreatic cysts have quite different characteristics from one another. Some of the kinds most often met with, or most important clinically, are these:

IPMN

Intraductal papillary mucinous neoplasm (IPMN) is a cystic lesion associated with the pancreatic ducts, which can produce a thick fluid called mucin.

IPMNs may be of the kinds that:

• Involve the main pancreatic duct,
• Develop from the side branches,
• Affect both together.

The risk of becoming cancer may be higher particularly in IPMNs involving the main pancreatic duct.

A substantial proportion of side-branch IPMNs, on the other hand, are low risk and can be followed with imaging in suitable patients.

Mucinous cystic neoplasm (MCN)

Mucinous cystic neoplasm is seen mostly in women and generally in the body or the tail of the pancreas.

Because it has the potential to become cancer, surgical treatment may come into consideration according to the size and structure of the cyst and the patient’s circumstances.

Serous cystadenoma

The great majority of serous cystadenomas are benign, and their risk of becoming cancer is extremely low.

Surgical treatment is usually not needed for serous cystadenomas with typical imaging features that cause no complaints.

Cysts that grow very large or press on neighbouring organs are assessed separately.

Pseudocyst

A pseudocyst is not a true cystic tumour.

It is a collection containing pancreatic fluid, generally appearing after acute or chronic pancreatitis.

That the patient has had pancreatitis before is an important clue to the diagnosis.

Not every pseudocyst has to be drained. Pseudocysts that cause complaints, become infected, enlarge or press on neighbouring organs may need interventional treatment.

Solid pseudopapillary neoplasm

This is rarer, and may appear particularly in young women.

Although “solid” appears in its name it may contain both solid and cystic parts. Its treatment mostly needs surgical assessment.

Does a pancreatic cyst turn into cancer?

This is one of the most important questions patients ask.

Most pancreatic cysts are not cancer. Nor does every pancreatic cyst turn into cancer.

But some mucin-producing cysts, particular kinds of IPMN and MCN especially, may over time show changes that can be precursors of pancreatic cancer.

So the main aim in following up pancreatic cysts is to identify in good time the cysts at high risk of becoming cancer, without carrying out unnecessary procedures on the low-risk ones.

Which features of a pancreatic cyst matter?

When a pancreatic cyst is assessed, its diameter alone is not what is looked at.

The doctor assesses in particular:

• The size of the cyst,
• Which part of the pancreas it is in,
• Its relationship to the main pancreatic duct,
• Whether the main pancreatic duct is widened,
• Whether there is a mural nodule or a solid part within the cyst,
• The characteristics of the cyst wall,
• Whether it has grown over time,
• Whether the patient has developed jaundice or pancreatitis.

The patient’s age, general state of health, family history and fitness for surgery also matter in reaching a decision.

Which findings call for more attention?

Some findings may call for the cyst to be examined in more detail.

For instance:

• The development of jaundice,
• A solid component or a mural nodule seen within the cyst,
• Marked widening of the main pancreatic duct,
• Marked enlargement of the cyst, or rapid growth during follow-up,
• Recurrent pancreatitis that may be related to the cyst,
• Certain large cysts,
• Suspicious imaging features

may call for a more detailed assessment.

The presence of one of these findings does not mean the person definitely has cancer. But it allows an assessment of whether further investigation is needed.

Does a pancreatic cyst cause symptoms?

Most pancreatic cysts cause no symptoms at all.

In some patients there may be:

• Upper abdominal pain or discomfort,
• Pain going through to the back,
• Nausea,
• Repeated attacks of pancreatitis.

Some lesions pressing on the bile duct or lying in the head of the pancreas can cause jaundice.

But because abdominal pain is very common in the population, it is not right to attribute all the abdominal complaints of a patient with a small pancreatic cyst automatically to the cyst.

How is a pancreatic cyst assessed?

Various imaging methods are used in assessing pancreatic cysts.

MR and MRCP

Magnetic resonance (MR) and MRCP are very important methods in assessing pancreatic cysts.

They help to show the cyst’s connection with the pancreatic ducts, the state of the main pancreatic duct, and the internal structure of the cyst.

Because they involve no radiation, they also offer an important advantage in patients who need long-term follow-up.

Computed tomography (CT)

CT is useful in assessing the pancreas and the surrounding structures.

It can give important information particularly about calcifications, some solid parts, and the general anatomy of the pancreas.

Why is an EUS done?

Endoscopic ultrasound (EUS) allows the pancreas to be imaged at high resolution from immediately alongside the stomach and duodenum, with a special endoscope carrying an ultrasound device at its tip.

EUS may be used particularly:

• Where the kind of cyst cannot be established with certainty on imaging,
• Where risky features are suspected,
• Where a nodule or a solid part within the cyst is being looked for,
• Where a more detailed assessment is needed.

An EUS is not needed for every pancreatic cyst.

Can fluid be taken from the cyst?

Yes. In some patients where it is thought necessary, a fluid sample can be taken from within the cyst during EUS using a fine needle.

This procedure is called EUS-guided cyst aspiration.

The fluid obtained can be assessed for:

• Certain biochemical markers,
• Examination of the cells (cytology),
• Molecular or genetic features where needed.

These tests can help to establish whether the cyst is mucinous, or whether it has features suspicious for becoming cancer.

But analysis of the cyst fluid is not on its own a method that gives a hundred per cent certain diagnosis either.

Should CA 19-9 be measured?

The serum CA 19-9 level can give useful information in assessing some pancreatic cysts.

But CA 19-9 is not a “cancer test”.

A high value does not necessarily mean that cancer is present, just as a normal value does not definitely exclude cancer.

The result is therefore assessed together with the imaging and the other clinical findings.

Should every pancreatic cyst be followed up?

No.

Whether follow-up is needed is decided according to the kind of cyst, its size, its imaging features, and the patient’s age and general state of health.

Some small, low-risk cysts can be followed at intervals with MR/MRCP.

In some cysts thought typically to be benign, long-term follow-up may not be needed.

The interval of follow-up is not the same in all patients.

If a cyst grows, does that mean it has become cancer?

No.

The growth of a cyst is a finding that needs to be assessed, but it does not on its own mean cancer.

What matters, alongside the rate of growth, is whether a new nodule or solid part has developed within the cyst, whether there has been a change in the pancreatic duct, and the patient’s clinical features.

For this reason comparing older MR or CT images with the new ones is very valuable.

When is a pancreatic cyst operated on?

Not every pancreatic cyst is operated on.

Operations on the pancreas are major surgical procedures. The benefit the operation will give is therefore weighed together with the risk the surgery will pose.

Surgery may come into consideration particularly for:

• Cysts where cancer is suspected,
• Those carrying a risk of high-grade cellular change,
• Those showing marked high-risk features,
• Certain mucinous cystic neoplasms,
• Selected cysts causing complaints or complications.

The decision should where possible be made by the joint assessment of teams experienced in gastroenterology, radiology, pathology and pancreatic surgery.

What should a person with a pancreatic cyst attend to?

One of the most important points is that the follow-up is not lost.

It helps for the patient to keep their older MR, CT and EUS reports. The change in the cyst over the years can then be assessed properly.

Reassessment is also needed in situations such as:

• Newly developed jaundice,
• Unexplained marked weight loss,
• New or increasing upper abdominal or back pain,
• Recurrent pancreatitis.

Should everyone with a pancreatic cyst be anxious?

No.

A substantial proportion of pancreatic cysts are low risk and never lead to a serious problem.

The real aim is to avoid both extremes:

It is not right to treat every cyst as cancer, creating needless fear and needless procedures.

Nor, conversely, is it right to treat a cyst with the potential to become cancer as entirely unimportant and leave it without follow-up.

The modern approach is follow-up and treatment individualised to the level of risk.

Remember

Seeing a cyst in the pancreas does not mean you have pancreatic cancer.

There are different kinds of pancreatic cyst, and their risks of becoming cancer differ greatly from one another.

The kind of cyst, its size, its relationship to the pancreatic duct, any nodules or solid areas within it, and its change over time should all be assessed together.

MR/MRCP and, where needed, EUS are important methods in establishing the characteristics of a cyst.

Not every pancreatic cyst needs a biopsy, an EUS or an operation. But it matters that the cysts that do carry risk are properly recognised and followed at appropriate intervals.