Solid pseudopapillary neoplasm of the pancreas

Solid pseudopapillary neoplasm of the pancreas (SPN) is a rare pancreatic tumor classified by the World Health Organization as a low-grade malignant neoplasm, characterized by generally slow growth but with a genuine potential for local invasion and metastasis. It is also known as “Frantz tumor” and is distinct from pancreatic ductal adenocarcinoma in its natural history, molecular biology and response to treatment. In most cases the disease is potentially curable with surgery, with high long-term survival rates even in selected advanced disease when appropriately treated.

Clinically, SPN predominantly affects young women, often of reproductive age, and is increasingly identified incidentally during ultrasonography or CT performed for other reasons. When symptomatic, presentation is driven more by mass effect and local complications than by systemic illness. Imaging typically shows a well-circumscribed lesion, often with solid and hemorrhagic-cystic components, but the radiologic appearance is not pathognomonic and requires a structured diagnostic pathway with pathologic confirmation.

Definitive diagnosis requires close integration of radiology, interventional endoscopy and pathology. The distinctive biologic feature is alteration of the Wnt pathway, almost always driven by CTNNB1 with nuclear accumulation of beta-catenin, accompanied by a typical immunophenotype that distinguishes SPN from neuroendocrine tumors, acinar cell carcinoma and other pancreatic neoplasms. Treatment centers on complete resection when feasible, whereas metastatic or recurrent cases require individualized multidisciplinary decisions.

The epidemiology of solid pseudopapillary neoplasm of the pancreas is defined by its rarity. In modern surgical series, SPN accounts for a small proportion of exocrine pancreatic neoplasms and a meaningful but still minority proportion of pancreatic cystic tumors. Its true incidence in the general population is difficult to estimate because some cases remain asymptomatic and are detected only as abdominal imaging becomes more common. Most information derives from retrospective series, institutional registries and systematic reviews, with variability related to diagnostic criteria, access to surgery and pathology standards.

Demographically, the most consistent association is with female sex and young adulthood. SPN may also occur in men and children, but less frequently; in these settings, diagnosis is often later because the pretest probability is perceived as lower and the histologic subtype may not be considered immediately in the radiologic differential diagnosis. The tumor may arise in any pancreatic segment; head-body-tail distribution varies among series, partly because of referral bias and incidental detection patterns.

The etiologic causes of SPN have not been defined. No environmental or infectious exposure has been shown to be necessary and sufficient to cause the disease, and no external trigger is universally recognized. The tumor’s biologic identity is instead strongly supported by a recurrent molecular signature, particularly activation of the Wnt pathway through CTNNB1, which describes a pathogenic mechanism but does not clarify the initiating event that triggers cellular transformation.

In the absence of a demonstrated etiology, risk factors also remain nonspecific. Female predominance has led to hypotheses involving hormonal signaling or tissue-microenvironment differences, but these observations do not identify a risk factor usable for population prevention. No characteristic hereditary pattern has been documented, and a general family history of cancer does not itself define increased SPN risk in clinical practice. Consequently, no clinically actionable risk profile for targeted prevention programs can currently be delineated.

For solid pseudopapillary neoplasm of the pancreas, there are no screening programs or population surveillance strategies. The main reasons are the combination of rarity and the lack of a noninvasive test with adequate performance. Unlike high-risk conditions for pancreatic carcinoma in specific genetic syndromes, SPN has no established clinical criteria for identifying a population that should undergo periodic imaging.

In clinical practice, early diagnosis occurs mainly through an incidental finding or investigations requested for nonspecific symptoms. In patients with persistent abdominal pain, pancreatic enlargement on imaging, obstructive jaundice or signs of local compression, pancreatic-protocol CT or MRI provides the initial assessment and guides possible further evaluation with endoscopic ultrasonography. In these scenarios, the objective is not “SPN screening” but appropriate evaluation of a pancreatic clinical-radiologic suspicion.

After surgical treatment, postoperative surveillance is reasonable because, although prognosis is often favorable, late recurrences and metastases occur in a minority of cases. No single universally standardized schedule exists; in practice, follow-up frequency and duration are tailored to individual risk, considering resection margins, histologic features of aggressiveness, vascular or perineural invasion and disease stage at surgery. Serial CT or MRI is generally the mainstay of surveillance, with particular attention to the liver and peritoneum.

SPN has distinctive biology that explains many clinical features, including its often slow growth and the feasibility of curative resection. The central pathogenic mechanism is dysregulation of the Wnt pathway, almost always driven by somatic CTNNB1, which causes nuclear accumulation of beta-catenin and transcriptional activation of target genes involved in proliferation, cell adhesion and phenotypic plasticity. This molecular driver is also one of the most useful diagnostic features because it produces a characteristic immunohistochemical pattern.

Morphologically, SPN often shows a mixed architecture, with solid areas and pseudopapillary structures generated by loss of cellular cohesion around a fibrovascular core. Intratumoral hemorrhage and cystic degeneration are common and contribute to the classic “solid-cystic” radiologic appearance. A capsule and expansile growth are frequent but do not exclude microscopic invasion in biologically more aggressive cases.

Immunophenotypically, diagnosis is based on an integrated panel demonstrating the Wnt/beta-catenin signature and a characteristic set of markers. Nuclear localization of beta-catenin is particularly informative, whereas positivity for markers such as CD10 and progesterone receptor is common and useful in distinguishing SPN from neuroendocrine and acinar neoplasms. Interpretation must always be contextualized with morphology and clinical-radiologic findings, particularly in cytologic specimens or limited biopsies.

Typical biologic features of SPN with diagnostic and clinical implications

• Recurrent CTNNB1 mutations with Wnt pathway activation and nuclear accumulation of beta-catenin.
• Morphology with solid areas and pseudopapillary structures, often with hemorrhage and cystic degeneration.
• Immunophenotype frequently positive for beta-catenin (nuclear), CD10, vimentin and progesterone receptor, providing a useful differential diagnostic pattern.
• Usually low-grade behavior, but with possible local invasion and metastases in a minority of cases.

Histology may show a broad spectrum of atypia; most SPNs retain a relatively indolent profile, but some display higher-risk features such as lymphovascular invasion, perineural infiltration, extrapancreatic extension and high mitotic activity. In such cases, distinguishing low-grade neoplasia from frankly aggressive behavior requires accurate pathologic description and multidisciplinary discussion, because it may influence follow-up intensity and duration and the use of additional treatments in selected settings.

The clinical manifestations of SPN are often subtle and depend mainly on lesion size and location. An increasing number of diagnoses are incidental during abdominal imaging performed for unrelated indications. When the mass becomes symptomatic, the most common presentation is vague abdominal pain or epigastric pressure, sometimes associated with nausea or reduced tolerance of meals.

Compression of adjacent structures may cause more specific symptoms. Lesions in the pancreatic head may be associated with obstructive jaundice or pancreatitis due to obstruction of the main pancreatic duct, whereas body-tail masses may present with back pain or a palpable finding in thin individuals. Intralesional hemorrhage and cystic degeneration may cause subacute worsening of pain or symptoms of peritoneal irritation in the event of rare but possible rupture.

Physical examination, especially in the early stages, may reveal no specific sign. A large tumor may occasionally be palpable as an abdominal mass. Laboratory findings are often nondiagnostic: no serum marker is specific for SPN, and common pancreatic tumor markers may be normal. Clinical recognition therefore depends mainly on correct interpretation of imaging and an appropriate indication for histologic confirmation when required.

Clinical presentations that most often prompt pancreatic investigation

• Incidental detection of a pancreatic mass with solid-cystic components in a young person, often female.
• Persistent or recurrent epigastric pain, sometimes with nausea and early satiety.
• Obstructive jaundice or pancreatitis, particularly with lesions in the pancreatic head.
• Palpable abdominal mass or distension in large tumors.

Overall, clinical findings rarely permit a subtype-specific diagnosis. SPN enters the differential diagnosis when age, sex and especially the radiologic pattern are suggestive; confirmation requires a structured diagnostic pathway and expert histologic assessment.

The diagnostic work-up for solid pseudopapillary neoplasm of the pancreas begins with radiologic suspicion of a pancreatic mass and proceeds through a sequence designed to define the nature of the lesion, resectability and histologic diagnosis. In most cases, the pathway starts with ultrasonography or CT performed for nonspecific symptoms or incidentally. When a pancreatic lesion is identified, the reference study is CT with a pancreatic protocol or, alternatively or as a complement, MRI with dedicated sequences and assessment of the biliary and pancreatic ducts.

CT accurately assesses size, vascular relationships and signs of invasion or metastases. MRI is particularly useful for characterizing cystic and hemorrhagic components, identifying fluid-fluid levels and defining lesion contents more clearly. SPN often appears as a well-circumscribed, frequently encapsulated mass with solid and cystic components, but this pattern overlaps with other entities, including mucinous cystic neoplasms, pancreatoblastoma in children, neuroendocrine tumors with cystic degeneration and acinar cell carcinoma. Therefore, when radiologic diagnosis is insufficiently reliable or when the result may alter treatment, further evaluation with endoscopic ultrasonography (EUS) is indicated.

Endoscopic ultrasonography permits high-resolution characterization and, above all, fine-needle aspiration or core-needle biopsy (EUS-FNA or EUS-FNB) to obtain diagnostic material. In resectable tumors with strongly suggestive imaging and a consistent clinical context, some centers may proceed directly to surgery; however, preoperative confirmation is particularly useful when observation is being considered, when alternative diagnoses require different treatments or when the lesion is atypical for the patient’s age or morphology.

Definitive diagnosis is pathologic. The surgical or biopsy specimen is assessed for solid-pseudopapillary architecture, hemorrhage, cystic degeneration and features of aggressiveness. Immunohistochemistry is central: nuclear beta-catenin positivity, together with CD10 and a targeted panel, supports the diagnosis and excludes the main alternatives, particularly neuroendocrine tumors. When indicated, molecular characterization may confirm CTNNB1 alterations and assist in problematic or recurrent cases rather than serving as a routine test.

According to the specialist literature, reliable diagnosis of SPN and appropriate treatment planning require:

Essential clinical and diagnostic steps

• Dedicated pancreatic-protocol CT or MRI to characterize the lesion and assess vascular relationships.
• Multidisciplinary evaluation to determine the indication for resection and the need for preoperative confirmation.
• Endoscopic ultrasonography with sampling (EUS-FNA or EUS-FNB) when the result may alter the strategy or imaging is inconclusive.
• Pathologic confirmation with compatible morphology and a typical immunophenotype, including beta-catenin nuclear staining within an integrated panel.
• Radiologic staging to exclude metastases and define resectability, with particular attention to the liver and peritoneum.

For preoperative staging, contrast-enhanced CT of the chest and abdomen is often sufficient. 18F-FDG PET is not routinely used in SPN and is considered case by case, particularly when biologic aggressiveness or an alternative diagnosis is suspected. In selected cases, CT angiography or MRI with detailed vascular assessment is useful for surgical planning, especially when the tumor is in close contact with the superior mesenteric artery, celiac trunk or portal vein, or when complex surgery is anticipated.

In summary, diagnosis originates from dedicated imaging, is consolidated by histologic and immunohistochemical confirmation when necessary, and is completed by accurate definition of disease extent and resectability to select the most appropriate treatment.

Staging of solid pseudopapillary neoplasm of the pancreas is challenging because most cases follow an indolent course and no staging system is universally dedicated to SPN. In clinical practice, extent is described in terms of local invasion, lymph-node involvement and metastases for prognostic and surgical purposes. When standardized nomenclature is required, for example for oncologic reporting, comparison among series or clinical communication, the AJCC/UICC TNM system (8th edition) for exocrine pancreatic tumors may be used, always specifying the SPN histologic subtype and its generally low-grade biology.

TNM size and vascular categories permit reproducible description of local extent, whereas nodal classification depends on the number of positive lymph nodes. Lymph-node involvement in SPN is uncommon compared with ductal adenocarcinoma, but when present it indicates more aggressive behavior and supports more intensive follow-up. Metastases, when they occur, primarily involve the liver and peritoneum and may develop years after surgery; prognosis should therefore be interpreted with the possibility of late recurrence in mind.

Stage groups for exocrine pancreatic carcinoma (AJCC/UICC 8th edition), useful as descriptive terminology for SPN when appropriate

• Stage 0: intraepithelial neoplasia or carcinoma in situ confined to the ducts (Tis), with no regional lymph-node metastases (N0) and no distant metastases (M0).
• Stage IA: tumor confined to the pancreas with a maximum diameter of ≤2 cm (T1), with no regional lymph-node metastases (N0) and no distant metastases (M0).
• Stage IB: tumor confined to the pancreas with a maximum diameter >2 cm and ≤4 cm (T2), with no regional lymph-node metastases (N0) and no distant metastases (M0).
• Stage IIA: tumor confined to the pancreas with a maximum diameter >4 cm (T3), with no regional lymph-node metastases (N0) and no distant metastases (M0).
• Stage IIB: tumor confined to the pancreas and measuring ≤2 cm (T1), >2 cm and ≤4 cm (T2), or >4 cm (T3), with regional lymph-node metastases in 1–3 nodes (N1) and no distant metastases (M0).
• Stage III: tumor confined to the pancreas and measuring ≤2 cm (T1), >2 cm and ≤4 cm (T2), or >4 cm (T3), with regional lymph-node metastases in ≥4 nodes (N2) and no distant metastases (M0), or tumor involving major arterial vessels (T4), with any regional lymph-node status (any N) and no distant metastases (M0).
• Stage IV: tumor of any local extent (any T), with any regional lymph-node status (any N) and distant metastases present (M1).

Prognosis in SPN is generally favorable after complete resection, with high long-term survival. However, a subgroup remains at risk of recurrence or metastasis, and individual prognosis depends on disease extent, achievement of negative margins, presence of metastases and histologic features of aggressiveness. It is clinically important to recognize that patients undergoing surgery even for selected metastatic disease may achieve prolonged survival, unlike in many other pancreatic neoplasms, making assessment at experienced centers essential.

Treatment of solid pseudopapillary neoplasm of the pancreas centers on surgery, which is the most effective intervention and is potentially curative in most cases. The choice of procedure depends on location, size, vascular relationships and suspected invasion, with the aim of achieving complete resection with negative margins while preserving pancreatic function whenever possible. Pancreaticoduodenectomy is more often used for lesions in the pancreatic head, whereas distal pancreatectomy is typical for body-tail tumors, with splenectomy as appropriate according to anatomic relationships and nodal suspicion.

In selected cases, particularly small, well-encapsulated tumors located away from the main pancreatic duct, parenchyma-sparing resections such as enucleation or segmental resection may be considered, balancing the risk of pancreatic fistula against the need for adequate margins. Extended lymphadenectomy is not standardized as it is in ductal carcinoma because nodal involvement is relatively uncommon; however, intraoperative findings and clinical suspicion may justify sampling or broader dissection when needed for staging and radicality.

Management of metastatic or recurrent disease requires a highly individualized approach. With limited liver metastases or localized recurrence, surgical resection or locoregional procedures may be considered in selected patients because long-term control may be achievable. Evidence for chemotherapy is limited and derives from small series and case reports; systemic therapy is considered mainly for unresectable, progressive or symptomatic disease, and regimen selection depends on the clinical profile and options available at specialist centers.

Treatment goals and options according to the clinical setting

• Localized and resectable disease: complete resection with negative margins, choosing the procedure according to location and ductal and vascular relationships.
• Locally advanced disease: multidisciplinary assessment of surgical feasibility, strategies to reduce operative risk and symptom control.
• Selected metastatic disease: consideration of resection of the primary tumor and metastases in patients with low-volume disease and good performance status.
• Perioperative support: pain management, nutritional optimization, and prevention and treatment of pancreatic fistula and pancreatic insufficiency.

Control of complications and perioperative support are central. Infection prevention, management of pancreatic fistula, assessment of endocrine and exocrine insufficiency and nutritional education improve outcomes and reduce long-term functional impact. In young patients, particular attention to preservation of pancreatic function and quality of life is integral to the treatment strategy.

Follow-up and post-treatment surveillance in SPN must account for two features: the high likelihood of cure after complete resection and the smaller but genuine possibility of late recurrence. No universally standardized protocols exist, but surveillance based on clinical visits, pancreatic functional assessment and periodic imaging is reasonable, with frequency and duration tailored to the individual risk profile.

During the first years after surgery, follow-up includes a targeted history for abdominal pain, weight loss, persistent nausea or symptoms suggestive of recurrence. Metabolic parameters should be monitored to detect endocrine insufficiency early, and signs of malabsorption should be assessed for exocrine insufficiency, particularly after extensive resections. Abdominal CT or MRI is used to document the absence of local recurrence and evaluate the liver and peritoneum, typical sites of disease relapse.

Closer and more prolonged follow-up is appropriate in cases with aggressive histologic features, uncertain margins or initially advanced disease. Surveillance is not based on specific serum markers; the choice of additional laboratory tests depends on the clinical picture and type of resection. The practical objective is to detect potentially resectable recurrence and manage functional sequelae of treatment promptly.

Long-term quality-of-life considerations after SPN treatment depend mainly on the type of pancreatic resection, patient age and the presence of pancreatic insufficiency. Because many patients are young and have a long life expectancy, functional consequences carry substantial weight and require proactive management. After distal pancreatectomy, the risk of diabetes and exocrine insufficiency is present but variable; after pancreaticoduodenectomy, digestive and nutritional sequelae may be more demanding and require stable dietary adaptations.

Exocrine pancreatic insufficiency may present with steatorrhea, bloating, weight loss and deficiencies of fat-soluble vitamins; pancreatic enzyme replacement and expert dietary support substantially improve quality of life and daily functioning. Endocrine insufficiency requires therapeutic education and diabetes follow-up, with particular attention in young adults to effects on work, sports and family planning.

Psychological well-being is often affected by the diagnosis of a rare tumor and the need for major surgery at a young age. Clear communication about the generally favorable prognosis, the rationale for follow-up and management of sequelae reduces anxiety and uncertainty. After extensive resections, nutritional rehabilitation and psychological support can facilitate return to a fully active life while preserving adherence to surveillance and continuity of care.

Complications of SPN arise mainly from mass effect, local complications and consequences of surgical treatment. Before resection, large tumors may cause persistent pain, common bile duct compression with jaundice, duodenal obstruction, pancreatitis or, more rarely, rupture with peritoneal irritation. Although most SPNs are well circumscribed, local invasion and metastases may occur in a minority of cases and contribute to distant complications, particularly in the liver and peritoneum.

After surgery, the most characteristic complication is postoperative pancreatic fistula, with a risk of collections, infection and delayed recovery. Other complications include bleeding, delayed gastric emptying after pancreaticoduodenectomy, pancreatitis of the pancreatic remnant, splenic or portal vein thrombosis in selected settings and wound complications. Over the long term, exocrine and endocrine pancreatic insufficiency is an important functional complication affecting nutrition and metabolism.

• Postoperative complications: pancreatic fistula, abdominal collections, infection, bleeding and delayed gastric emptying after pancreatic head resections.
• Functional complications: exocrine pancreatic insufficiency with malabsorption and weight loss; endocrine insufficiency with new-onset diabetes.
• Complications of advanced disease in rare aggressive cases: local recurrence and liver or peritoneal metastases causing pain, ascites or organ dysfunction.

Prevention and management of complications rely on careful selection of the surgical procedure, perioperative care at high-volume centers, early monitoring for signs of fistula and targeted functional follow-up. Early nutritional and metabolic care reduces symptom burden and supports return to stable long-term quality of life.