Solid pseudopapillary neoplasm and other rare pancreatic tumours
Solid pseudopapillary neoplasm is an uncommon pancreatic tumour with a distinctive profile: it occurs overwhelmingly in young women, it is usually large by the time it is found, and — unlike almost every other solid pancreatic tumour — it is curable by surgery in the great majority of cases. Patients told they have a pancreatic tumour often assume the worst, and for this diagnosis that assumption is usually wrong.
How it forms
The cell of origin remains uncertain, which is unusual for a tumour this well characterised. It does not correspond neatly to ductal, acinar or endocrine tissue, and one hypothesis is an origin from cells of the genital ridge that became incorporated into the pancreas during development — a suggestion supported by the tumour's strong female predominance and by its frequent expression of progesterone receptors.
What is established is the molecular mechanism: almost all of these tumours carry a mutation in CTNNB1, the gene encoding beta-catenin, causing abnormal accumulation of beta-catenin in the nucleus. This is a defining feature and is used diagnostically.
The tumour grows slowly as a well-circumscribed mass, often with a fibrous capsule. Its characteristic appearance arises because the poorly supported cells furthest from blood vessels degenerate, leaving surviving cells clustered around vessels in a pattern that resembles papillae under the microscope — hence "pseudopapillary" — and producing areas of haemorrhage and cystic change within an otherwise solid tumour. This mixed solid-and-cystic appearance with haemorrhage is what suggests the diagnosis on imaging.
It is classified as a tumour of low malignant potential. A small proportion behave more aggressively, with local invasion or spread to the liver or peritoneum, but even in those patients resection produces good long-term outcomes.
Symptoms
Most present with vague abdominal discomfort or a palpable mass, and a substantial proportion are found incidentally. Because the tumour tends to displace surrounding structures rather than invade them, it may become large before causing much trouble. Occasionally a tumour presents acutely with pain from haemorrhage into it, or after abdominal trauma ruptures it.
How the diagnosis is made
CT and MRI show a well-defined, encapsulated mass with both solid and cystic components and evidence of internal haemorrhage. The combination of these features in a young woman is strongly suggestive.
Endoscopic ultrasound with biopsy confirms it. Immunohistochemistry is characteristic — nuclear beta-catenin staining, together with a typical pattern of other markers — and reliably distinguishes it from neuroendocrine tumours, which are the main alternative and which it can resemble on imaging.
The distinction is not academic. A neuroendocrine tumour, an adenocarcinoma and a solid pseudopapillary neoplasm sitting in the same position carry entirely different prognoses and different operations.
Treatment
Complete surgical resection is the treatment, and in most patients it is curative. The operation is dictated by position — distal pancreatectomy for the body or tail, pancreaticoduodenectomy for the head.
Two considerations specific to this tumour shape the surgery. First, the patients are typically young women with a normal pancreas and a long life ahead, so preserving pancreatic tissue and the spleen matters more here than in an older patient with cancer; parenchyma-sparing approaches such as enucleation or central pancreatectomy are considered where the tumour's position allows. Second, because the tumour rarely spreads to lymph nodes, extensive lymphadenectomy is not required, which permits a less radical operation.
Where limited spread to the liver or peritoneum exists, resection of those deposits is still worthwhile — long-term survival remains achievable, which is not the case for most metastatic pancreatic tumours. Chemotherapy and radiotherapy have little established role.
Other rare pancreatic tumours
Acinar cell carcinoma arises from the enzyme-producing cells. It may cause raised serum lipase, and in a minority produces a syndrome of subcutaneous fat necrosis, joint pain and eosinophilia from circulating lipase. It is more aggressive than solid pseudopapillary neoplasm but has a better outlook than ductal adenocarcinoma, and resection is the mainstay.
Pancreatoblastoma is the commonest pancreatic tumour of childhood, rare in adults, and is treated with resection combined with chemotherapy.
Lymphoma and metastases to the pancreas — from renal cell carcinoma in particular, sometimes many years after the original nephrectomy — are important because they are treated quite differently from a primary pancreatic tumour. Renal metastases to the pancreas can be resected with good results. This is a further reason that tissue diagnosis matters when the picture is atypical.
Recovery
As for other pancreatic resections, determined by the operation performed. Distal pancreatectomy typically means five to eight days in hospital; pancreaticoduodenectomy, eight to fourteen. Young patients with an otherwise healthy pancreas generally recover well and often retain normal endocrine and exocrine function where enough gland has been preserved.
Follow-up
Imaging surveillance is arranged, as late recurrence is described, though uncommon. Follow-up is generally less intensive than for adenocarcinoma, reflecting the far better prognosis.
When to seek a specialist opinion
Any pancreatic mass in a young patient, and any mass with mixed solid and cystic components or evidence of internal haemorrhage, should be assessed by a specialist pancreatic unit before conclusions are drawn. The essential point is that a pancreatic tumour is not synonymous with pancreatic cancer, and establishing which tumour is present — before treatment is planned and before a patient is given a prognosis — changes everything that follows.
Common questions
I have been told I have a rare pancreatic tumour. Is that bad news?
Not necessarily, and in the case of solid pseudopapillary neoplasm it is generally good news. It is a low-grade tumour occurring mostly in young women, it rarely spreads, and complete removal cures the great majority. Being told a tumour is rare is not the same as being told it is aggressive.
Why do these tumours occur almost entirely in young women?
The reason is not fully established, though the tumour cells consistently show an abnormality in the beta-catenin signalling pathway, and hormone receptors are frequently present, which may explain the strong female predominance. It is not caused by anything you have done.
How is it distinguished from other pancreatic tumours?
By the combination of the patient's age and sex, a characteristic appearance on scanning — a well-defined mass with both solid and cystic areas, often with haemorrhage — and confirmation on tissue sampling, where nuclear staining for beta-catenin is diagnostic. The distinction matters, because the treatment and the outlook differ completely from pancreatic ductal cancer.
Do I need chemotherapy or radiotherapy?
Almost never. Complete surgical removal is the treatment, and no additional therapy is required in the great majority. Chemotherapy is reserved for the rare cases with widespread disease.
How much pancreas will be removed?
As little as safely possible. Because these tumours are usually well defined and rarely involve lymph glands, a limited resection — or occasionally simply shelling the tumour out — is often sufficient, and extensive surgery with lymph gland clearance is not required. Preserving the spleen is also usually possible, which matters for long-term immunity.
Will I be able to have children afterwards?
Yes. The operation does not affect fertility, and a limited pancreatic resection in a young woman generally leaves normal pancreatic function. Pregnancy after treatment is not restricted.
Can it come back?
Uncommonly, and usually years later, which is why follow-up scans continue for several years. Recurrence, when it occurs, is often confined to one site and can be removed again with good results.
What about the other rare tumours mentioned?
They behave very differently from one another, which is why establishing the exact diagnosis matters more than the fact of rarity. Some, like lymphoma involving the pancreas, are treated with drugs rather than surgery — operating on them would be the wrong treatment entirely. This is one of the reasons a tissue diagnosis is obtained before a major operation where the appearances are unusual.
Related conditions
Other conditions of the pancreas covered on this site:
- Pancreatic ductal adenocarcinoma
- Acute pancreatitis
- Chronic pancreatitis and its complications
- Pancreatic cysts — IPMN and MCN
- Pancreatic neuroendocrine tumours
- Periampullary lesions
- Pancreas divisum
- Annular pancreas
This page provides general information and does not replace an individual medical consultation. Assessment and treatment are decided for each patient after review of their history, examination and imaging, and in the setting of a multidisciplinary team.