Pancreatic cysts are being commonly discovered owing to the increased use of diagnostic techniques like ultrasound scans of the abdomen, CT Scans and MRI. These diagnostic tests are routinely performed for other reasons. Pancreatic cysts are thought to be present in 3% to 15% of our population. This prevalence of the condition increases with advancing age. When such cysts are identified, they create significant anxiety for the clinician and the patient owing to the potential spectre of a deadly cancer. In the past, inflammatory non-cancerous pseudocysts were thought to be the commonest ones, but in the past two decades the increasing use of advanced imaging techniques like CT and MRI scans have led to the diagnosis of non-inflammatory (neoplastic) cysts. At the time of initial discovery these neoplastic cysts are smaller than the inflammatory cysts which often have a history of acute pancreatitis. On many occasions, additional testing may be necessary to supplement the CT or MRI scans to determine the nature of these cysts.
Types of cysts
Cystic lesions of the pancreas can be categorised broadly into two types, namely Non-neoplastic (E.g.: Pseudocysts) and Neoplastic cystic lesions. The second variety are termed as Cystic Neoplasms of the Pancreas. This variety is further broadly divided into those that produce mucin (a protein containing substance present in mucous secretions) and those that don’t. This difference is important, as it is the mucin producing cysts which are the likeliest to be cancers. An example of such mucin producing tumours which can then turn cancerous is IPMN (Intraductal Papillary Mucinous Neoplasm). An example of a cystic tumour which does not turn cancerous is serous cystadenoma. Papillary cystic neoplasms (e.g., solid pseudopapillary tumours of the pancreas) and cystic pancreatic neuroendocrine tumours are additional examples of cystic neoplasms of the pancreas.
The biggest challenge faced by doctors is to differentiate between these types of cysts depending on their potential to turn into cancers by carrying out the least invasive diagnostic methods. Multiple guidelines exist on the management of these cysts which are consensus based, but there is a little agreement on an evidence based approach in medical literature thus far.
These types of pancreatic cysts were thought to be the commonest historically (>90%). But newer techniques of imaging have increased the rate at which neoplastic cysts are diagnosed. The critical issue is to differentiate between inflammatory cysts and those with a potential to turn into a cancer. The most common clinical indicator to indicate the benign nature of the cyst is to determine whether the patient has had a history of pancreatitis or there is an associated solid mass. In a few instances the cyst may be the cause for the pancreatitis, especially when it is associated with a subtle mass which may be picked up only on Endoscopic Ultrasound examination. Generally, a review of the imaging studies done during the acute episode of pancreatitis helps in diagnosing the nature of the cyst.
Small fluid filled compartments make up these cysts. The term “microcystic adenoma” is a synonym for this type of cyst. These occur more commonly in women who present with the condition in their 60s. If similar cysts are noted in a younger woman, the possibility of a malignancy is often higher and a thorough diagnostic evaluation may be necessary. An aggressive variant “malignant serous cystadenocarcinoma” is rarely noted. Patients may present with symptoms when there is an increase in size or there is evidence of invasion into the surrounding tissues. Surgeons do suggest removal of the cyst when such features are noted on radiological investigations.
Mucinous Cystic Neoplasms
These types of cysts comprise of nearly 50% of all the cystic tumours excised by surgical interventions in most contemporary surgical series. They occur almost exclusively in women and are diagnosed in their 40s and 50s.
They may or may not present with abdominal symptoms of pain and bloating but a majority are diagnosed on incidental CT or MRI imaging.
They are characterised by a typical architecture which resembles ovarian stoma – spindle cell stroma. The cysts are lined by mucin producing duct-like cells featuring a papillary architecture. However, they may be misdiagnosed as “pseudocysts” due to the denudation of the cyst lining.
These types of cysts may have a cancerous component in up to one third of the cases and in such cases the survival is approximately 60% at the end of 5 years, which is like that of patients with pancreatic cancer.
Intraductal papillary mucinous neoplasms (IPMN) are also mucin producing cysts which communicate with the main Pancreatic duct as their main point of distinction from Mucinous cystic neoplasms. These include a category of cysts which were in the past called mucinous ductal ectasia. These cysts are precursors of malignancy in all instances. However, the time taken to develop into a cancer is not well elucidated. They are sub classified depending on the type of cells which make up the lining of the papilla.
These cysts occur commonly in men with the mean age of diagnosis in the mid 60s. They are frequently seen in the head of the pancreas and usually present with recurrent episodes of pancreatitis, with ductal dilatation and symptoms which resemble chronic pancreatitis.
IPMN may involve the main duct or the side branches and mixed variants are also noted. IPMN involving the main duct do not necessary lead to cyst formation whereas side branch and mixed IPMNs exhibit cyst formation.
Surgical excision with a negative margin on pathology offers excellent survival in these cystic tumors.
Less Common Cystic Lesions
- Cystic pancreatic Neuroendocrine tumours
- Papillary Cystic tumours
Clinical Approach to Cysts
- A detailed history – look for history of pancreatitis
- Previous Cross sectional imaging including CT and MRI scans have to be reviewed to determine any change in the size and nature of the cyst.
- Small lesions are often asymptomatic.
- Vague symptoms of fullness, pain.
- Typical symptoms of cancer are usually absent.
- Jaundice may not be a presenting symptom.
Questions the surgeon needs to answer
- Is the cyst Neoplastic?
- If it is Neoplastic what is the risk of progression to Cancer?
- Does upfront surgery balance against the long-term risk of malignancy?
- Does surgery provide any long-term survival benefit to the patient?
Tools for the Surgeon Before Deciding on Surgery
- CT Scan
- MRI Scan
- Endoscopic Ultrasound with Fine Needle Aspiration Cytology
- Analysis of the cyst fluid for tumour markets like CEA, CA 19-9
Depending on the nature of the cyst and the probability of the presence of a cancer an appropriate surgical approach is chosen. These may include Pancreaticoduodenectomy (Whipple’s procedure), Central Pancreatectomy, Distal pancreatectomy or Total pancreatectomy. In patients with IPMN multiple frozen sections by the pathologist may be needed intra-operatively to determine if the cut margins are free of the cancer.
Pancreatic cysts are being increasingly encountered in our day to day practice owing to better imaging techniques. Identifying whether the cyst has a potential to turn into a cancer is of great importance but is not easily achieved with routine evaluation. Surgery to excise the cyst is the only method to achieve cure. Judicious utilisation of the surgical approach is essential to obtain optimal results.