Solid pseudopapillary tumor of the pancreas:A systematic review of clinical,surgical and oncological characteristics of 1384 patients underwent pancreatic surgery

Background:Pancreatic solid pseudopapillary tumors(SPTs)are rare clinical entity,with low malignancy and still unclear pathogenesis.They account for less than 2%of exocrine pancreatic neoplasms.This study aimed to perform a systematic review of the main clinical,surgical and oncological characteristics of pancreatic SPTs.Data sources:MEDLINE/PubMed,Web of Science and Scopus databases were systematically searched for the main clinical,surgical and oncological characteristics of pancreatic SPTs up to April 2021,in accordance with the preferred reporting items for systematic reviews and meta-analyses(PRISMA)standards.Primary endpoints were to analyze treatments and oncological outcomes.Results:A total of 823 studies were recorded,86 studies underwent full-text reviews and 28 met inclusion criteria.Overall,1384 patients underwent pancreatic surgery.Mean age was 30 years and 1181 patients(85.3%)were female.The most common clinical presentation was non-specific abdominal pain(52.6%of cases).Mean overall survival was 98.1%.Mean recurrence rate was 2.8%.Mean follow-up was 4.2 years.Conclusions:Pancreatic SPTs are rare,and predominantly affect young women with unclear pathogenesis.Radical resection is the gold standard of treatment achieving good oncological impact and a favorable prognosis in a yearly life-long follow-up.

Unraveling the enigma:A comprehensive review of solid pseudopapillary tumor of the pancreas

Solid pseudopapillary tumor of the pancreas(SPTP)is a rare neoplasm predom-inantly observed in young females.Pathologically,CTNNB1 mutations,β-catenin nuclear accumulation,and subsequent Wnt-signaling pathway activation are the leading molecular features.Accurate preoperative diagnosis often relies on imaging techniques and endoscopic biopsies.Surgical resection remains the mainstay treatment.Risk models,such as the Fudan Prognostic Index,show promise as predictive tools for assessing the prognosis of SPTP.Establishing three types of metachronous liver metastasis can be beneficial in tailoring individu-alized treatment and follow-up strategies.Despite advancements,challenges persist in understanding its etiology,establishing standardized treatments for unresectable or metastatic diseases,and developing a widely recognized grading system.This comprehensive review aims to elucidate the enigma by consolidating current knowledge on the epidemiology,clinical presentation,pathology,molecular characteristics,diagnostic methods,treatment options,and prognostic factors.

Pathological differential diagnosis of solid-pseudopapillary neoplasm and endocrine tumors of the pancreas

AIM:To investigate differential points of solid-pseudo-papillary neoplasm (SPN) of the pancreas and pancre-atic endocrine tumor (PET).METHODS:Ten cases of SPN and fourteen cases of PET were studied in this retrospective study. Clinical and pathologic features,immunostaining reactions and β-catenin gene mutations were analyzed.RESULTS:The mean age of SPN patients was 25.6 years and these patients had no specific symptoms. The mean diameter of the tumors was 11.0 cm,9/10 cases were cystic or a mixture of solid and cystic structures,and there was hemorrhage and necrosis on the cut surface in 8/10 (80%) cases. Characteristic pseudo-papillary structure and discohesive appearance of the neoplastic cells were observed in all 10 (100%) cases. The results of immunostaining showed that nuclear expression of β-catenin and loss of E-cadherin in all the cases,was only seen in SPN. Molecular studies discov-ered that 9/10 (90%) cases harbored a point mutation of exon 3 in β-catenin gene. On the other hand,the mean age of PET patients was 43.1 years. Eight of 14 cases presented with symptoms caused by hypoglyce-mia,and the other 6 cases presented with symptoms similar to those of SPN. The mean size of the tumors was 2.9 cm,most of the tumors were solid,only 3/14 (21%) were a mixture of solid and cystic structures,and macroscopic hemorrhage and necrosis were much less common (3/14,21%). Histologically,tumor cells were arranged in trabecular,acinar or solid patterns and demonstrated no pseudopapillary structure and discohesive appearance in all 14 (100%) cases. The results of immunostaining and mutation detection were completely different with SPN that membrane and cytoplastic expression of β-catenin without loss of E-cadherin,as well as no mutation in β-catenin gene in all the cases. CONCLUSION:Both macroscopic and microscopic features of SPN are quite characteristic. It is not difficult to distinguish it from PET. If necessary,immunos-taining of β-catenin and E-cadherin is quite helpful to make the differential diagnosis.

Diagnosis and treatment of solid-pseudopapillary tumor of the pancreas

BACKGROUND: Solid-pseudopapillary tumor (SPT) of the pancreas is a rare exocrine pancreatic tumor. Despite the increasing recognition of the tumor in recent years, its pathogenesis and apparent therapeutic algorithm remain unclear. This study was designed to define the clinical, imaging, and pathologic features and to improve the diagnosis and treatment of this rare disease. METHOD: The clinical, imaging, and pathologic findings of 9 SPT patients managed in our hospital between 2001 and 2005 were retrospectively analyzed, and related literatures were reviewed. RESULTS: In the 9 patients aged from 14 to 68 years, 8 were female and 1 male. The mean age of these patients at diagnosis was 30 years. Initially, 8 patients complained of vague abdominal pain and one patient had pancreatic mass detected incidentally by abdominal CT. The levels of blood and urine amylase and tumor markers were all within the normal range. B-US, CT and MRI demonstrated that tumors were well encapsulated and contained some degree of internal hemorrhage or cystic degeneration. The mean transverse diameter of these tumors was 5.4 cm (range, 2-10.5 cm). The tumors were located at the head (2 patients), body (2), body and tail junction (4), and tail (1) of the pancreas. Surgical procedures included pancreaticoduodenectomy, distal pancreatectomy, distal pancreatectomy with splenectomy, and enucleation. Histological examination showed solidified cystic areas and papillary protrusions. Two malignant tumors demonstrated retroperitoneal metastases and vascular invasion. Follow-up for 2.5 years on average showed that one patient died of tumor recurrence at 10 months and the rest were alive. CONCLUSIONS: SPT exhibits unique clinical and pathologic features and is readily diagnosed by its characteristic imaging and histological appearance. Surgical resection of the primary tumor and metastases is the treatment of choice.

Endoscopic ultrasound-guided fine-needle aspiration cytology diagnosis of solid pseudopapillary tumor of the pancreas: A case report and literature review

We describe the clinical, imaging and cytopathological features of solid pseudopapillary tumor of the pancreas (SPTP) diagnosed by endoscopic ultrasound- guided (EUS-guided) fine-needle aspiration (FNA). A 17-year-old woman was admitted to our hospital with complaints of an unexplained episodic abdominal pain for 2 mo and a short history of hypertension in the endocrinology clinic. Clinical laboratory examinations revealed polycystic ovary syndrome, splenomegaly and low serum amylase and carcinoembryonic antigen (CEA) levels. Computed tomography (CT) analysis revealed a mass of the pancreatic tail with solid and cystic consistency. EUS confirmed the mass, both in body and tail of the pancreas, with distinct borders, which caused dilation of the peripheral part of the pancreatic duct (major diameter 3.7 mm). The patient underwent EUS-FNA. EUS-FNA cytology specimens consisted of single cells and aggregates of uniform malignant cells, forming microadenoid structures, branching, papillary clusters with delicate fibrovascular cores and nuclear overlapping. Naked capillaries were also seen. The nuclei of malignant cells were round or oval, eccentric with fine granular chromatin, small nucleoli and nuclear grooves in some of them. The malignant cells were periodic acid Schiff (PAS)-Alcian blue (+) and immunocytochemically they were vimentin (+), CA 19.9 (+), synaptophysin (+), chromogranin (-), neuro-specific enolase (-), a1- antitrypsin and a1-antichymotrypsin focal positive. Cytologic findings were strongly suggestive of SPTP. Biopsy confirmed the above cytologic diagnosis. EUS- guided FNA diagnosis of SPTP is accurate. EUS findings,cytomorphologic features and immunostains of cell block help distinguish SPTP from pancreatic endocrine tumors, acinar cell carcinoma and papillary mucinous carcinoma.

Solid-Pseudopapillary Tumor: Case Report and Literature Review

Solid-pseudopapillary tumor of the pancreas (SPT) or Frantz’s tumor is a rare epithelial neoplasm that represents 0.3% to 2.7% of exocrine pancreatic tumors. These tumors occur mainly in young women and have a good prognosis. We present a case of a 19-year-old female patient who presented to the emergency for abdominal pain. Physical examination reveals a left hypochondrium mass. Ultrasound imaging showed an encapsulated caudal pancreatic mass with cystic components. The patient underwent tumor excision and lymph node removal. Macroscopically, the tumor was encapsulated and measuring 12 × 8 × 7 cm. It has a solid-cystic and hemorrhagic appearance inside. Histologically, the tumor had two components: solid and papillary. Tumor tissue showed monomorphic tumor cells radiating around blood vessels. Perineural invasion and vascular emboli were not seen. Three lymph nodes without metastases were observed. The diagnosis of solid-pseudopapillary tumor of the pancreas (SPT) or Frantz’s tumor was retained. Solid-pseudo-papillary tumor of the pancreas is rare and not always suspected by the physician. The clinical and imaging patterns are not specific. Anatomopathological examination confirmed the diagnosis. The patient underwent curative surgery.

Solid pseudopapillary tumor of the pancreas:A review of 553 cases in Chinese literature

AIM:To sum up the clinical and pathological characte- ristics of solid pseudopapillary tumor (SPT) and the experience with it.METHODS: A total of 553 SPT patients reported in Chinese literature between January 1996 and January 2009 were retrospectively reviewed and analyzed. RESULTS: The mean age of the 553 SPT patients included in this review was 27.2 years, and the male to female ratio was 1:8.37. Their symptoms were non-specific, and nearly one third of the patients were asymptomatic. Computed tomography and ultraso-nography were performed to show the nature and location of SPT. Most of the tumors were distributed in the pancreatic head (39.8%), tail (24.1%), body andtail (19.5%). Forty-five patients (9.2%) were diagnosed as malignant SPT with metastasis or invasion. None of the clinical factors was closely related to the malignant potential of SPT. Surgery was the main therapeutic modality for SPT. Local resection, distal pancreatectomy and pancreatoduodenectomy were the most common surgical procedures. Local recurrence and hepatic metastasis were found in 11 and 2 patients, respectively, after radical resection. Four patients died of tumor progression within 4 years after palliative resection of SPT. The prognosis of SPT patients was good with a 5-year survival rate of 96.9%.CONCLUSION: SPT of the pancreas is a rare indolent neoplasm that typically occurs in young females. It is a low-grade malignancy and can be cured with extended resection. The prognosis of such patients is good although the tumor may recur and metastasize.

Prediction of malignancy and adverse outcome of solid pseudopapillary tumor of the pancreas

Since solid pseudopapillary tumor of the pancreas(SP-TP) was officially classified by the World Health Org-anization in 1996,SPTP has recently received special attention in the literature.Studies have shown that SPTP is a heterogeneous tumor,with a small percentage of patients harboring aggressive behaviors.However,cri-teria for malignancy grade in SPTP have not been well established.The prognosis of SPTP is generally good,with cases having a chance for long-term survival even with recurrence and/or metastasis after surgical resection.The current American Joint Committee on Cancer/Union for International Cancer Control tumor,node,metastasis staging system is not specific to SPTP.The lack of a pre-dictive staging classification that accurately describes the heterogeneity of this disease hinders meaningful research into optimal individualized therapy.Here we summarize and discuss the associated factors proposed for appraisal of the malignant potential and adverse outcome of SPTP.

Solid-pseudopapillary tumor of the pancreas: Clinical experience and literature review

AIM: To evaluate the clinical presentations of solidpseudopapillary tumor of the pancreas (SPT) and examine the diagnosis, treatment, low grade malignant potential of this rare disease.METHODS: We retrospectively reviewed a series of seven patients with SPT managed in our hospital between July 1990 and October 2003. Six females and one male with mean age of 31 years (range 13 to 50 years) were diagnosed with SPT at our institution.RESULTS: Clinical presentation included a palpable abdominal mass in two patients and vague abdominal discomfort in another two. Two patients were asymptomatic;their tumors were found incidentally on abdominal sonographic examination for other reasons. The final patient was admitted with hemoperitoneum secondary to tumor rupture. The mean diameter of the tumors in the seven patients was 10.5 cm (range 5 to 20 cm). The lesions were located in the body and tail in five cases and in the head of the pancreas in two. Surgical procedures included distal pancreatectomy (3), distal pancreatectomy with splenectomy (2), pancreaticoduodenectomy (1) and a pylorus-preserving Whipple procedure (1). There were gross adhesions or histological evidence of infiltration to the adjacent pancreas and/or splenic capsule in four cases. None of the patients received adjuvant therapy.The mean follow up was 7 years (range 0.5 to 14 years).One patient developed multiple liver metastases after 14 years of follow up.CONCLUSION: SPT is a rare tumor that behaves less aggressively than other pancreatic tumor. However, in cases with local invasion, long-term follow up is advisable.

Clinicopathological study of solid and pseudopapillary tumor of pancreas: Emphasis on magnetic resonance imaging findings

AIM: To report the clinicopathological features and magnetic resonance imaging (MRI) findings of solid and pseudopapillary tumor (SPT) of pancreas.METHODS: From 1981 to 2005, 26 surgically treated cases of SPT were retrospectively reviewed. MRI findings of the latest 11 consecutive SPT cases were investigated.RESULTS: There were 25 women and one man having SPT (median age: 23 year) with a median tumor size of 7.5 cm. Among them, nine patients developed solid pseudopapillary carcinoma. During the median follow-up period of 66 mo, the 5-year survival rate of the 26 SPT patients was 96.2%. Three MRI features were proposed including Type 1 image, displaying SPT with completely solid part. All SPT patients with type 1 image were detected incidentally. Type 2 image displays of SPT with solid mass hemorrhage and type 3 image with massive hemorrhage. All the eight SPT patients with type 2 and 3 images suffered abdominal pain due to hemorrhage from SPT.CONCLUSION: SPT had a favorable survival rate irrespective of surgical procedures, malignancy, and MRI findings, however, MRI could reliably correlate with its clinicopathological features.

Imaging features of solid pseudopapillary tumor of the pancreas on multi-detector row computed tomography

AIM:To retrospectively analyze the imaging features of solid-pseudopapillary tumors(SPTs) of the pancreas on multi-detector row computed tomography(MDCT) and define the imaging findings suggestive of malignant potential.METHODS:A total of 24 consecutive cases with surgically and pathologically confirmed SPTs of the pancreas underwent preoperative abdominal MDCT studies in our hospital.All axial CT images,CT angiographic images,and coronally and sagittally reformed images were obtained.The images were retrospectively reviewed at interactive picture archiving and communication system workstations.RESULTS:Of the 24 cases of SPTs,11 cases(45.8%) occurred in the pancreatic head and seven(29.1%) in the tail.Eighteen were pathologically diagnosed as benign and six as malignant.MDCT diagnosis of SPTs was well correlated with the surgical and pathological results(Kappa = 0.6,P < 0.05).The size of SPTs ranged from 3 to 15 cm(mean,5.8 cm).When the size of the tumor was greater than 6 cm(including 6 cm),the possibilities of vascular(8 vs 1) and capsular invasion(9 vs 0) increased significantly(P < 0.05).Two pathologically benign cases with vascular invasion and disrupted capsule on MDCT presented with local recurrence and hepatic metastases during follow-up about 1 year after the resection of the primary tumors.CONCLUSION:Vascular and capsular invasion with superimposed spread into the adjacent pancreatic parenchyma and nearby structures in SPTs of the pancreas can be accurately revealed by MDCT preoperatively.These imaging findings are predictive of the malignant potential associated with the aggressive behavior of the tumor,even in the pathologically benign cases.

Solid pseudopapillary tumor of the pancreas in male patients: Report of 16 cases

AIM:To investigate the clinical characteristics,surgical strategies and prognosis of solid pseudopapillary tumors(SPTs)of the pancreas in male patients.METHODS:From July 2003 to March 2013,116 patients were diagnosed with SPT of the pancreas in our institution.Of these patients,16 were male.The patients were divided into two groups based on gender:female(group 1)and male(group 2).The groups were compared with regard to demographic characteristics,clinical presentations,surgical strategies,complications and follow-up outcomes.RESULTS:Male patients were older than female patients(43.1±12.3 years vs 33.1±11.5 years,P=0.04).Tumor size,location,and symptoms were comparable between the two groups.All patients,with the exception of one,underwent complete surgical resection.The patients were regularly followed up.Themean follow-up period was 58 mo.Two female patients(1.7%)developed tumor recurrence or metastases and required a second resection,and two female patients(1.7%)died during the follow-up period.CONCLUSION:Male patients with SPT of the pancreas are older than female patients.There are no significant differences between male and female patients regarding surgical strategies and prognosis.

Pancreatic panniculitis and solid pseudopapillary tumor of the pancreas: A case report

Solid pseudopapillary tumor of the pancreas(SPTP), also known as solid and papillary epithelial neoplasm of the pancreas, is a rare pancreatic exocrine tumor that is difficult to diagnose before surgery. Pancreatic panniculitis is a rare type that occurs in less than 3% of all patients with pancreatic diseases. We here report a 19-year-old woman who presented with persistent left upper quadrant pain without obvious cause for 1 d. The patient also developed subcutaneous nodules involving lower abdomen bilaterally and lower limbs, and subcutaneous nodules were pathologically diagnosed as pancreatic panniculitis. Plain abdominal computed tomography revealed a soft-tissue mass in the body and tail of the pancreas, which was closely associated with the gastric wall. Contrast-enhanced ultrasound showed inhomogeneous echogenicity in the anterior pancreatic body, which had blurred parenchymal demarcation of the body and tail of the pancreas. Contrast-enhanced abdominal computed tomography revealed a mixed density mass with solid and cystic components in the body and tail of the pancreas, and the solid component was markedly enhanced. The lesion was pathologically diagnosed as SPTP after laparoscopic resection. Clinicians should be aware of the clinical manifestation, diagnosis, and treatment of pancreatic panniculitis and SPTP.

Clinical analysis of solid-pseudopapillary tumor of the pancreas:report of 15 cases

BACKGROUND: Solid-pseudopapillary tumor of the pancreas (SPTP) is an uncommon and enigmatic pancreatic neoplasm that occurs mainly in young women. Although more and more cases have been reported in recent years, misdiagnosis and incorrect treatment still frequently take place. This study was designed to stimulate consideration of this tumor. METHODS: We retrospectively reviewed the experience of diagnosis and treatment of 15 patients with SPTP and compared them with 516 patients with pancreatic cancer from January 1997 to March 2007. RESULTS: Most of the SPTP cases were asymptomatic except for one palpable mass. Almost all SPTPs demonstrated a solid structure with hypo- or isoattenuation, cystic structure with hypo-attenuation on precontrast CT scan, and enhancement of solid portions on post-contrast CT scan. By contrast, most cases of pancreatic carcinoma had multiple symptoms and abnormal blood results. The tumors showed hypo-attenuation on both precontrast and post-contrast CT scan, and only a few showed iso-attenuation on post-contrast CT scan. All cases of SPTP in our group were cured by surgical resection, while only 16.86% of patients with pancreatic carcinoma could undergo a radical resection. CONCLUSIONS: Clinical features and CT scans were helpful to differentiate SPTP from pancreatic carcinoma. Radical surgical resection was the most effective and safe method for the treatment of SPTP.

A case of solid pseudopapillary tumor of the pancreas

We present ultrasound, computed tomography and magnetic resonance imaging findings in a case with pancreatic solid pseudopapillary tumor and their correlations with histopathology. Ultrasound revealed a hypoechogenic mass, and computed tomography revealed a hypodense mass at the pancreatic head minimally enhanced after intravenous contrast agent administration. Magnetic resonance imaging showed a hypointense mass on unenhanced T1-weighted images including a hyperintense focus representing the hemorrhage. The lesion was hyperintense on T2- weighted images. On the postcontrast images the lesion showed peripheral thin contrast enhancement in arterial phase and enhanced slightly diffusely in venous and equilibrium phases. The patient underwent elective resection of the mass and pancreatoduodenectomy with jejunostomy tube placement. A final diagnosis of solid pseudopapillary tumor was made histopathologically. Solid pseudopapillary tumor is a rare pancreatic tumor. It is important to make the diagnosis preoperatively because with an adequate surgical resection the prognosis is good. A multimodalitary approach, especially magnetic resonance imaging can suggest the diagnosis without the need for biopsy.

Combined treatment for solid pseudopapillary tumor of the pancreas with liver metastasis

Solid pseudopapillary tumor (SPT) of the pancreas is a rare pancreatic disease. Generally, it is considered a benign or low-grade malignant tumor. SPT of the pancreas with liver metastasis or invasion to adjacent organs is usually uncommon.

Retroperitoneal congenital epidermoid cyst misdiagnosed as a solid pseudopapillary tumor of the pancreas:A case report

BACKGROUND Retroperitoneal cysts are rare and usually asymptomatic abdominal lesions.Epidermoid cysts are frequent benign cutaneous tumors,but retroperitoneal localization of these cysts does not occur very often.CASE SUMMARY We report a case report of a 25-year-old woman with a giant mass in the abdominal cavity.Because imaging examination indicated that the mass probably originated from the pancreas,the mass was considered a solid pseudopapillary tumor of the pancreas(SPTP).However,surgery revealed a retroperitoneal epidermoid cyst located behind the pancreas neck and the root of the superior mesenteric artery(SMA).We performed complete resection of the tumor.Postoperative pathology showed an epidermoid cyst.The patient fared well after two months of follow-up.CONCLUSION Surgery is the gold standard for the diagnosis and treatment of retroperitoneal epidermoid cysts.Retroperitoneal epidermoid cysts around the pancreas are easily misdiagnosed as cystic SPTPs.Surgeons should pay particular attention to preoperative diagnosis to reduce severe surgical complications and improve the quality of life of patients.

Cryoablation for liver metastasis from solid pseudopapillary tumor of the pancreas: A case report

BACKGROUND Solid pseudopapillary tumor(SPT) of the pancreas is a rare pancreatic tumor and 10% to 15% of cases are associated with metastasis. Cryoablation is a new method that can induce tumor necrosis, and treatment of tumors by cryoablation can cause anti-tumor immune responses.CASE SUMMARY A 16-year-old woman with SPT of the pancreas developed liver metastases 5.3 years after complete resection of the primary pancreatic tumor. She was admitted with chief complaints of abdominal pain in the upper abdomen and a weight loss of approximately 5 kg over 4 mo. Carbohydrate antigen(CA) 125,carcinoembryonic antigen, and CA 199 were normal. An abdominal computed tomography scan found multiple nodules in the right lobe of the liver that measured approximately 13.5 cm × 10.8 cm × 21.4 cm. Immunohistochemical staining results showed that CD10 and CD56 were positive, and the patient was diagnosed with SPT of the pancreas with liver metastasis. The patient underwent percutaneous cryoablation and interventional embolization. During the 5-year follow-up, the patient remained disease-free after cryoablation, with relatively normal immune function.CONCLUSION Herein, we for the first time report the treatment of liver metastasis from SPT of the pancreas using cryoablation plus interventional embolization, which could be a promising alternative therapy for pancreatic SPT liver metastasis.

The clinicopathological and immuohistochemical analysis of solid-pseudopapillary tumor of the pancreas:report of 9 cases

Objective：To investigate the clinical features, pathological characteristics and immunophenotype of solid-pseudopapillary tumor of the pancreas（SPTP）. Methods：Nine surgically treated cases of SPTP were retrospectively reviewed. Hematoxylin and Eosin（HE） staining and immunohistochemical staining were used to analyze all cases, and the general clinical data was collected. Results：Six patients were asymptomatic except for a palpable mass. Two patients complained of vague-epigastric pain. One patient appeared jaundice. The tumor was encapsulated and solid tissues alternately with cystic tissues. Histologically, the histological structure of solid portion was pseudopapillary with a fibrovascular core. Tumor cells were uniform and medium-sized which were arranged in sheets ets or nests or pseudopapillary patterns. Immunohistochemical studies demonstrated that SPTP proved positive in vimentin（9/9 cases）, AAT（9/9 cases）, NSE（9/9 cases）, ACT（7/9 cases）, CK20（2/9 cases）, CgA（1/9 cases）, S-100（3/gcases）, PR（4/gcases）, Syn（3/9 cases） and CD56（5/9cases）, negative in CEA and ER. Conclusion：SPTP is a tumor predominantly occurring in young women frequently without special symptoms. This tumor has various characteristical histological patterns with different immunophenotype.

Solid-Pseudopapillary Tumor of the Pancreas:One Case Report and Literatures Review

IntroductionSolid-pseudopapillary tumor(SPT)is a very rare primary neoplasmof the pancreas.Franz first described it in 1959.It is usually seen inyoung females.In spite of possible histological findings of malignan-cy,SPPT typically shows a benign clinical course and a low malig-nant potential.The pathogenesis of these tumors is still controversial.It has been suggested that it might originate from ductal and acinarpancreatic cells,endocrine cells or pluripotential stem cells.