- “Daughter” lesion, young asymptomatic non-Caucasian women
- Solid/cystic/necrotic/haemorrhagic encapsulated mass, pancreatic tail.
- Low-grade malignant potential (liver mets.). Good surgical outcome.
Description
Solid pseudopapillary neoplasm (SPN) of the pancreas, also known as solid pseudopapillary tumour (SPT) or Frantz’s tumour, is a rare type of pancreatic tumour. This neoplasm has a low malignant potential and is most commonly diagnosed in young women. SPNs account for a small fraction of pancreatic neoplasms but are important due to their unique characteristics and generally favourable prognosis. These tumours are characterised by an intriguing mixture of solid and cystic areas, with pseudopapillary structures that are not true papillae but rather degenerative features within the solid areas. The etymology of “pseudopapillary” highlights the tumour’s appearance, resembling papillae but without a true fibrovascular core.
Pathogenesis
The pathogenesis of SPN is not well understood, but these tumours are thought to originate from pluripotent pancreatic cells capable of both exocrine and endocrine differentiation. Genetic studies have identified mutations in the β-catenin gene (CTNNB1) in a significant number of SPNs, suggesting a role in tumorigenesis. These mutations lead to accumulation of β-catenin in the nucleus and cytoplasm, contributing to the neoplastic process.
Subtypes
There are no formal subtypes of SPN.
Epidemiology, Risk Factors & Associations
- Predominantly affects young, non-Caucasian women (90% female, mean age at diagnosis is approximately 30 years).
- Rare, accounting for 1-2% of all pancreatic neoplasms.
- No specific risk factors have been identified due to the tumour’s rarity.
Clinical Features
- Many patients are asymptomatic and diagnosed incidentally on imaging studies.
- Symptoms, when present, are often nonspecific and may include abdominal pain, a palpable abdominal mass, or nausea.
- Rarely, the tumour may rupture or bleed, leading to acute symptoms.
Complications
- Malignant transformation is rare but can occur, leading to metastasis, most commonly to the liver or peritoneum.
- Risk of complications related to tumour size and location, including obstruction of the biliary tract or duodenum.
Pathological Features
Histopathology
- Macroscopic: Well-circumscribed, encapsulated mass with solid and cystic components. Hypervascular capsule.
- Microscopic: Mixture of solid areas with pseudopapillary structures, characterised by cells around delicate vasculature, often with haemorrhagic and necrotic changes.
Serology
- Not specific for SPN.
Biochemistry
- Not specific for SPN.
Radiological Features
General Features
- Characteristically demonstrates a large well-circumscribed, mass with a combination of solid and cystic components and enhancing capsule.
- Typically located in pancreatic tail.
- Dystrophic calcifications may be present but are not common.
CT
- Non-contrast: May show a well-demarcated mass with varying degrees of internal density.
- C+ Arterial and C+ Venous: Enhancement of the solid components with possible delayed enhancement of the capsule.
MRI
- T1: Solid components are hypointense or isointense to pancreas; cystic components may have high signal intensity if haemorrhage is present. Fibrous capsule low signal.
- T2: High signal intensity in cystic, necrotic and haemorrhagic components. Fibrous capsule low signal.
- FLAIR, DWI/ADC, T1 Gad+: Enhances solid components and capsule.
- SWI/GRE/T2*: May highlight haemorrhage or calcifications.
US
- B-mode: Well-defined heterogenous mass with mixed solid and cystic components. Hypoechoic centre suggests necrosis/haemorrhage. Cystic portion may show fluid-debris level
- Colour Doppler: No internal vascularity
Grading and Staging
There is no formal grading or staging system for SPN, but the size of the tumour, presence of capsular invasion, and metastasis can influence prognosis.
Diagnosis
The diagnosis of SPN is based on a combination of imaging features and histopathological confirmation. Immunohistochemical staining positive for β-catenin and vimentin supports the diagnosis.
Differential Diagnosis
- Pancreatic adenocarcinoma: Typically presents in older adults and has a more aggressive behaviour.
- Pancreatic neuroendocrine tumours: May show similar imaging features but have different histological characteristics.
- Pancreatic cystic lesions: Include serous cystadenomas, mucinous cystic neoplasms, and intraductal papillary mucinous neoplasms, which have different clinical implications and management.
Management
Surgical resection is the treatment of choice for SPN, offering a good prognosis even in cases with metastasis. Complete surgical excision is associated with excellent long-term survival. Follow-up imaging is recommended to monitor for recurrence, especially in cases where complete resection was not achieved or if there was evidence of invasive behaviour.