Pancreatic Cysts

Pancreatic cysts are fluid-filled sacs within the pancreas. With the widespread use of cross-sectional imaging, they are now one of the most common incidental findings in the abdomen. The challenge is that while most are benign, some carry a real risk of cancer. Sorting one from the other requires a systematic approach in a high-volume unit with the full range of multidisciplinary expertise — which is precisely what Prof. Mittal and his team at the Australian Pancreatic Centre provide.

Why pancreatic cysts matter

Approximately 20 different types of pancreatic cyst have been described, but five account for over 90% of all cases. Their behaviour ranges from completely harmless to frankly malignant. Even among those with malignant potential, the timeline can span years, which means there is a genuine window to identify concerning lesions early and intervene before cancer develops. The cornerstone of good care is accurate diagnosis, appropriate risk stratification, and a clear plan — whether that means surveillance, further investigation, or surgery.

Types of pancreatic cysts

Pancreatic pseudocyst

Pseudocysts are collections of enzyme-rich pancreatic fluid enclosed by a wall of fibrous tissue, without an epithelial lining. They develop in up to a quarter of patients who have had pancreatitis, usually appearing at least four weeks after the acute episode. Most are single lesions, and nearly all pseudocysts smaller than 4 cm resolve on their own. Those larger than 10 cm, however, rarely resolve without intervention. Symptoms include abdominal pain and early satiety from gastric or duodenal compression. Complications such as infection, rupture, or bleeding from pseudoaneurysms of adjacent arteries can occur.

Management: Intervention is indicated when a pseudocyst causes symptoms, is enlarging, or is larger than 5 cm and hasn't shrunk after six weeks. Minimally invasive endoscopic drainage (with EUS-guided stent placement) is the preferred first-line treatment. Larger or dependent pseudocysts may require laparoscopic or open drainage.

Serous cystic neoplasm (SCN)

Serous cystic neoplasms are glycogen-rich lesions with extremely rare malignant potential. They account for 10–15% of pancreatic cystic neoplasms and mainly affect women in their 50s and 60s. On imaging they have a characteristic honeycomb or spongy appearance from their microcystic architecture, and a central calcified scar is often visible. Most SCNs remain stable over time, though up to a third may show slow growth of about 4 mm per year.

Management: Because these are almost always benign, a conservative approach with surveillance is appropriate for most patients. Resection is reserved for large symptomatic lesions, diagnostic uncertainty on imaging and EUS, or rapid growth. Once resected, no long-term follow-up is needed (except in the exceedingly rare circumstance of SCN-associated malignancy).

Mucinous cystic neoplasm (MCN)

Mucinous cystic neoplasms are mucin-producing lesions that carry a 15% risk of harbouring malignancy. They almost exclusively affect women (20:1 female-to-male ratio), typically in their 40s, and arise in the body or tail of the pancreas. On imaging they appear as thick-walled, septated macrocystic lesions, sometimes with peripheral calcifications. Features associated with higher malignant risk include septations, cyst-wall enhancement, larger size (especially >4 cm), and the presence of mural nodules.

Management: Resection is recommended for all surgically fit patients with MCN. Timely surgery is curative when no invasive component is present; five-year disease-specific survival drops to 57% once malignancy has developed. Patients with completely resected non-invasive MCN do not need long-term follow-up.

Intraductal papillary mucinous neoplasm (IPMN)

IPMN is a mucin-producing lesion arising from the ductal system of the pancreas, accounting for 15–30% of cystic neoplasms. It affects men and women equally, usually in their 60s. IPMNs are classified by the duct of origin: main-duct IPMN involves the main pancreatic duct and carries the highest malignant risk; branch-duct IPMN arises from side branches and has a lower but still real risk; mixed-type IPMN involves both. The lining epithelium can also show varying grades of dysplasia (low, intermediate, or high). The critical prognostic factor is whether invasive carcinoma has developed — IPMN-associated invasive cancer has a better prognosis (45% five-year survival) than conventional pancreatic ductal adenocarcinoma (15%), largely because it tends to be detected earlier.

Management: The presence of high-risk stigmata (obstructive jaundice, enhancing solid component in the cyst, or main pancreatic duct ≥10 mm) warrants surgical resection in fit patients. Worrisome features (cyst ≥3 cm, thickened enhancing walls, main duct 5–9 mm, non-enhancing mural nodule, or abrupt duct calibre change with distal atrophy) mandate further evaluation with EUS and fine-needle aspiration. Lesions without any worrisome features enter a size-based surveillance program. Surgery typically involves partial pancreatectomy (Whipple or distal pancreatectomy) with frozen-section margin assessment.

Solid pseudopapillary neoplasm (Frantz tumour)

This is a rare, indolent tumour with both cystic and solid components, primarily affecting young women (mean age 22 years, 10:1 female predominance). These lesions are often large at diagnosis and may cause abdominal pain or a palpable mass. Metastatic disease is present in only 6% of cases at presentation. On cross-section they appear heterogeneous with haemorrhagic cysts interspersed among pale solid tumour.

Management: Complete surgical resection is curative in 85–95% of patients. Importantly, even metastatic disease does not preclude resection — unlike pancreatic ductal adenocarcinoma, long-term survival is possible even with metastases because of the indolent biology of this tumour. Patients without invasive features require no long-term follow-up after resection.

Diagnostic workup

Every patient with a newly diagnosed pancreatic cyst should undergo a structured assessment. The goals are to determine the likely cyst type, identify any features that raise concern, and plan next steps.

Blood tests

Initial blood work includes full blood count, electrolytes and renal function, liver function tests, C-reactive protein, lipase, and the tumour marker CA 19-9. Elevated inflammatory markers with pain and fever raise concern for an infected pseudocyst. Deranged liver function may suggest bile duct compression from a head-of-pancreas lesion. A persistently elevated lipase after pancreatitis should prompt investigation for pseudocyst formation. An elevated CA 19-9 raises concern for an associated pancreatobiliary malignancy.

Imaging

Triple-phase (pancreatic protocol) CT with fine slices through the pancreas is the minimum imaging study. It identifies septations, nodules, calcifications, and the relationship to surrounding vessels for surgical planning.

Gadolinium-enhanced MRI with MRCP (magnetic resonance cholangiopancreatography) better defines the relationship of the cyst to the pancreatic duct — critical for distinguishing branch-duct IPMN from other cystic lesions. MRI is also preferred for younger patients requiring long-term surveillance, as it avoids cumulative radiation exposure.

Endoscopic ultrasound (EUS) and fine-needle aspiration

EUS involves passing an echoendoscope into the stomach and duodenum to visualise the entire pancreas in fine detail. It is indicated for cysts with worrisome features and for cysts larger than 3 cm even without such features. EUS-guided fine-needle aspiration obtains cyst fluid for cytology, carcinoembryonic antigen (CEA), and amylase analysis:

• CEA >192 ng/mL is highly predictive of a mucinous lesion (MCN or IPMN)
• High amylase usually indicates communication with the pancreatic duct (pseudocyst, IPMN)
• Low CEA and low amylase are characteristic of serous cystic neoplasm

EUS is operator-dependent and carries procedural risks including perforation and haemorrhage; it must be performed in a unit with high-volume expertise.

Risk stratification: when to watch, when to act

The decision between surveillance and surgery hinges on features seen on imaging. Lesions are stratified into three categories:

Surveillance protocol

For cysts without worrisome or high-risk features, surveillance is guided by the size of the largest cyst:

All surveillance should be conducted under the supervision of a pancreatic surgeon within a multidisciplinary team. Pseudocysts are followed with six-monthly imaging until symptoms resolve and a clear trajectory toward resolution is established.

Surgical treatment

When surgery is indicated, the procedure is tailored to the lesion. For lesions in the body or tail, a distal pancreatectomy (with splenectomy when necessary) is the standard approach. For lesions in the head of the pancreas, a pancreaticoduodenectomy (Whipple procedure) is performed. Frozen-section analysis of the resection margin ensures no high-grade dysplasia or malignancy is left behind.

Prof. Mittal uses advanced minimally invasive and robotic techniques where appropriate, which can reduce post-operative pain, shorten hospital stay, and speed recovery. Total pancreatectomy is reserved for highly selected cases because of the significant long-term metabolic consequences.

After resection, follow-up depends on the pathology. Patients with completely resected non-invasive MCN, serous cystic neoplasm, or solid pseudopapillary neoplasm without invasive features do not require long-term surveillance. IPMN patients need follow-up of the remnant pancreas because IPMN can be multifocal — those with a disease-free remnant are scanned at two and five years; those with residual IPMN continue size-based surveillance. Any cyst with an invasive component is followed according to pancreatic cancer protocols.

Why a high-volume pancreatic unit matters

Pancreatic cyst management sits at the intersection of gastroenterology, radiology, pathology, oncology, and surgery. Getting the diagnosis right and knowing when to operate — or when not to — requires experience that only comes from seeing a high volume of these lesions. The Australian Pancreatic Centre at Royal North Shore Hospital brings together all these disciplines in a single multidisciplinary team, with the imaging, endoscopic, and surgical expertise to provide comprehensive care. Every patient with a pancreatic cyst benefits from early referral to such a unit, where a structured, evidence-based plan can be developed and executed.