Pancreatic Cysts

Introduction

Pancreatic cysts are collections of fluid that form within the pancreas*.

The incidence of pancreatic cysts is increasing and most cysts are identified incidentally on imaging; indeed, around 15% of individuals going for abdominal MRI scan will have an incidental pancreatic cyst identified.

*Pancreatic cysts are divided into true cysts (non-inflammatory) and pseudocysts (inflammatory), however this article will only focus on true cysts

Figure 1 – The parts of the pancreas

Cyst Subtypes

Pancreatic cysts can be classified by secretions, by histology, or by risk of malignancy (as shown below). As a general rule, serous cysts are lower risk and mucinous cysts are higher risk. 

High Risk
Intraductual Papillary Mucinous Neoplasm Associated with pancreatic duct malignancies, often found at the main or branch pancreatic ducts
Mucinous Cystic Neoplasm Often found in the body or tail of the pancreas; 30% are cancerous on diagnosis and the remainder considered precancerous
Solid Pseudopapillary Neoplasm Rare cystic lesions, most commonly found in young Asian and Afro-Caribbean women; they have an excellent prognosis post-resection
Cystic Pancreatic Neuroendocrine Tumour Rare, frequently non-functional, associated with MEN 1 syndrome
Low Risk
Serous Cystic Adenoma Serous benign lesions, typically with a honeycombed appearance on imaging, most commonly found in the tail and body of pancreas
Simple Cyst The true epithelial cyst, are always benign lesions
Mucinous Non-Neoplastic Cyst Mucin producing lesions, dysplasia rarely found in these lesions
Lymphoepithelial Cyst Benign sheets of lymphocytes rarely with dysplastic cells associated

Clinical Features

Figure 2 – Histology of a Benign Mucinous Cystic Neoplasm

In 70% of cases, pancreatic cysts are asymptomatic, found incidentally on imaging.

For symptomatic cysts, presenting complaints include abdominal pain or back pain (from mass effect and compression symptoms), post-obstructive jaundice, or vomiting.

Cysts can become infected and present with systemic features. Those that become malignant and metastasise may present with systemic features of malignancy (weight loss, loss of appetite, change in bowel habits etc.)

Examination will likely be unremarkable; in rare occasions, there may be a tender abdomen, a palpable mass, or abdominal distension.


Differential Diagnoses

Pancreatic pseudocyst – this is a collection of fluid within the pancreatic tissue, typically forming following pancreatitis; the inflammatory reaction produces a necrotic space in the pancreas that fills with pancreatic fluid, however this lacks epithelial or endothelial cells surrounding the collection so is termed a pseudocyst. Pseudocysts are also commonly asymptomatic, so tend to be picked up on imaging.


Investigations

As suggested, most cases are picked up via imaging, however those cases being worked up for further management may warrant baseline blood tests, including FBC, U&Es, and LFTs. A CA 19-9 level can be helpful to monitor progression of the disease.

CT imaging (Figure 3) or MRI imaging of the abdomen are commonly the imaging modalities that identify the pancreatic cysts initially, MRI imaging being the more sensitive of the two.

Figure 3 – Pancreatic Cyst (marked with C) identified on CT scan, with associated fluid level (arrow) seen in the pancreatic tail

Low Risk Vs. High Risk on Imaging

Imaging can be used to stratify those cysts that are low risk versus those that are high risk.

  • Low risk features
    • Cyst diameter <3cm
    • Cystic morphology with central calcification
    • Asymptomatic
  • High risk features
    • Cyst diameter >3cm
    • Main pancreatic duct dilatation greater than 10mm
    • Enhancing solid component
    • Non-enhancing mural nodule

Based on the features identified on initial imaging, further investigation may be warranted, either via complete resection (especially if high risk) or further testing through Endoscopic US scan with Fine Needle Aspiration (EUS-FNA). EUS- FNA allows for a biopsy sample to be obtained, which is useful in determining both low and high grade lesions.


Management

Most pancreatic cysts will be discussed at the multidisciplinary team (MDT) meetings, to plan for any further imaging, follow-up, or surgical intervention warranted. The majority of pancreatic cysts are benign and can therefore be left alone with surveillance only.

In high-risk cysts, resection should be the first line of treatment, where feasible. There is no current consensus on the surveillance of pancreatic cysts following surgery, however in most cases a follow-up MRI scan every 2 years is reasonable.

In those with low risk cysts, surveillance is recommended every 5 years, as the risk of malignant transformation is so low (put at 0.24% per year). Any rapid growth or suspicions during surveillance should be re-investigated and managed appropriately.


Prognosis

The prognosis of these patients is highly dependent on subtype of the cyst and degree of invasion. Non-malignant and non-invasive cysts will have excellent prognosis, however malignant and invasive cysts have a significantly worse survival of 60% at 5-years, despite treatment.

Quiz

Question 1 / 3
How do most pancreatic cysts present?

Quiz

Question 2 / 3
Which of the following is deemed high risk on imaging

Quiz

Question 3 / 3
For a low risk cyst, what is the risk of malignant transformation each year?

Results

Further Reading

Pancreatic Cyst Disease: A Review
Stark A et al., JAMA

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