Rare Pancreatic Tumor Research Articles

Invasive Pancreatic Adenocarcinoma with Squamous Differentiation Arising in an IOPN with Novel MDM2 Amplification

Abstract Introduction/Objective Intraductal oncocytic papillary neoplasms (IOPNs) are rare pancreatic tumors that are genetically distinct from intraductal papillary mucinous neoplasms (IPMNs). Morphologic and molecular characterization of invasive adenocarcinomas associated with IOPNs remains limited due to the rarity of this entity. Methods/Case Report We present a 68-year-old female who initially presented with abdominal pain and jaundice. MRI revealed a 2.6 cm mass in the pancreatic head with abutment of the superior mesenteric vein and dilation of the biliary and pancreatic duct. Biopsy revealed adenocarcinoma with mucinous features. The patient was started on gemcitabine and abraxane. Her treatment course was complicated by biliary and duodenal obstruction requiring common bile duct and duodenal stenting. Surgical management with pancreaticoduodenectomy was performed six months following initial diagnosis. Gross examination revealed a 2.5 cm ill-defined tumor surrounding the main pancreatic duct adjacent to the common bile duct. Microscopy revealed an IOPN arising within the pancreatic duct exhibiting a complex papillary growth pattern. There was an associated moderately to poorly differentiated invasive carcinoma with mucinous and squamous differentiation with lymph node metastasis. Molecular testing (FoundationOne®CDx) revealed ARID1A mutation and amplification of MDM2, CDK4, and ERBB3. Patient is alive and without radiologic evidence of disease recurrence at 6 months follow-up. Results (if a Case Study enter NA) NA Conclusion To our knowledge, our case is the first report of an invasive pancreatic adenocarcinoma with squamous differentiation arising in association with an IOPN. In addition, our case showed MDM2 amplification which has not been previously identified in pancreatic adenocarcinoma arising in IOPNs. Although recent literature demonstrated that less than 30% of IOPN showed invasive disease and even fewer cases with lymph node metastasis, our case showed extensive invasion with metastases to 2 lymph nodes. This may suggest that MDM2 amplification may play a role in more aggressive disease since it is implicated with poorer outcome in conventional pancreatic adenocarcinoma. Further molecular studies of IOPN may help to identify prognostic features of this entity.

Undifferentiated carcinoma of the pancreas with osteoclast-like giant cells: a case report

BackgroundUndifferentiated carcinomas of the pancreas with osteoclast-like giant cells (UCPOGC) are rare pancreatic neoplasms that account for less than 1% of all pancreatic malignancies. This case report of a 54-year-old male with metastatic UCPOGC adds to the existing literature and further ascertains the clinical and imaging features, treatment options, and prognosis of this rare entity.Case presentationWe present the detailed clinical course of a 54-year-old Asian male patient with UCPOGC, with focus on the relevant clinical features and imaging findings that are characteristic of this disease entity.ConclusionsUCPOGC is an extremely rare pancreatic tumor with a unique histopathology and clinical course. It is often difficult to distinguish UCPOGCs from other pancreatic tumors, such as traditional pancreatic ductal adenocarcinomas (PDAC), on imaging, and it therefore remains a pathological diagnosis. Surgery is generally regarded as the first-line treatment option, and the roles of chemotherapy and radiation are unclear. Due to the exceeding rarity of this tumor, large-scale clinical studies are not feasible. Therefore, it is important to share individual insights and experiences to improve our understanding and care for patients with this devastating disease.

Gene expression profiling of pancreatic neuroendocrine carcinoma and mixed neuroendocrine-non-neuroendocrine neoplasm

Pancreatic neuroendocrine carcinoma (NEC) and mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) are rare pancreatic malignant tumors, and comprehensive gene analyses are scarce. In this study, six NECs and six MiNENs were collected, immunohistochemistry for synaptophysin, chromogranin A, INSM1, Ki-67, and Rb was conducted, and KRAS mutational status was examined. Among these cases, comprehensive gene expression analysis of oncogene pathways using nCounter® were performed with six NECs and four MiNENs, and those data were compared with that of three pancreatic ductal adenocarcinomas (PDACs), with that of three normal pancreatic ducts, and with each other. By dividing NEC and MiNEN cases into KRAS-mutated group and KRAS-wild group, the difference of clinicopathological data and gene expression profiling data were examined between the two groups. Compared to the data of normal pancreatic epithelium, all 13 cancer-related pathways were upregulated in PDAC, MiNEN, and NEC group with more upregulation in this order. Compared to the data of PDAC, genes of DNA Damage repair pathway was most upregulated both in NECs and MiNENs. Regarding the difference between KRAS-mutated and KRAS-wild groups, several genes were differentially expressed between the two, where MMP7 was the upregulated gene with highest p-value and NKD1 was the downregulated gene with highest p-value in KRAS-mutated group. From the extent of upregulation of 13 pathways, MiNEN was considered more progressed stage than PDAC, and NEC was considered more progressed than MiNEN. From the comparison of KRAS-mutated and KRAS-wild NECs and MiNENs, several differentially expressed genes were identified in this study.

Organ-preserving enucleation in a case of solid pseudopapillary neoplasm of pancreas

Solid pseudopapillary neoplasm (SPN) is a rare pancreatic tumor affecting mostly females in the second or third decade of life. These tumors have a low malignant potential, and hence, surgical resection remains the main treatment. Large tumors may present with compressive symptoms such as abdominal pain or vomiting. Once resected completely, SPNs usually have an excellent long-term prognosis. We report a 16-year-old girl who presented with vomiting and abdominal pain localized to the right upper quadrant. Imaging showed an encapsulated tumor arising from the pancreatic head which prompted us to perform organ-preserving enucleation. Histopathology confirmed the tumor as an SPN.

THU530 What Works For Ferret, Works For Man

Abstract Disclosure: P.J. Bhatt: None. S. Bendaram: None. V. Kantorovich: None. Insulinomas are rare pancreatic neuroendocrine tumors with an incidence of 4 cases per million per year and present with hypoglycemic symptoms due to uncontrolled and excessive insulin secretion by the tumor. Although most commonly benign and treated with surgery, 5-10% are malignant, inoperable and are managed medically with somatostatin analogs, chemotherapy, mTOR inhibitors and diazoxide. A 28 year old male with a history of metastatic insulinoma with progressive disease and refractory hypoglycemia presented with lethargy, diaphoresis, and blood glucose (BG) level of 32mg/dL [65-99]. He was previously admitted for severe hypoglycemia and was treated with FOLFOX, LUTATHERA, Octreotide, TPN, steroids and diazoxide suspension. Sugars were monitored via continuous glucose monitor (CGM) and insulin and C-peptide levels were closely monitored outpatient. Treatment was effective and medications were tapered off so that he no longer needed a CGM and was only on FOLFOX and octreotide prior to presentation. On admission, insulin level was 172 uIU/mL [<17], peaking at 312 uIU/mL and BG dropping to 22mg/dL. He was placed on a dextrose 10% infusion, TPN, diazoxide suspension, and CGM. This admission, however, his insulin levels were much higher requiring higher doses of diazoxide, but he was unable to tolerate the diazoxide solution due to extreme nausea and projectile vomiting, resigning him to a long-term stay in the ICU. Due to a lack of availability of other oral formulations in the US, compounding pharmacies were contacted and pharmaceutical grade diazoxide powder was compounded into 100mg capsules by an outside pharmacy. Dose was adjusted while monitoring BG and insulin levels. Prior to discharge, insulin level was 77.7 uIU/mL and BG levels had normalized. He was sent home on diazoxide 200mg twice a day, TPN, and CGM. FOLFOX was resumed. Outpatient follow up revealed euglycemia and suppressed insulin level of 12.3 uIU/mL [<17], allowing for further tapering of diazoxide dose and discontinuation of TPN. Diazoxide is known to be a safe and effective treatment for hypoglycemia in humans and ferrets alike. It inhibits insulin secretion in pancreatic B cells and increases hepatic glucose production. Side effects of nausea and vomiting can be a barrier to compliance, as seen in our patient. Currently, only oral solutions of diazoxide have been approved for human consumption whereas ferrets, commonly afflicted with insulinomas, are treated with oral pills. Changing the oral formulation to pill form allowed for better compliance, easy dose adjustments using insulin as a marker for response, and symptom resolution due to adequate suppression of insulin levels. Most importantly, it allowed for our patient to transfer out of the ICU and be discharged home with improved quality of life, a feat that was impossible without this change in formulation. Presentation: Thursday, June 15, 2023

SAT152 Retrospective Analysis Of HbA1c In Patients Diagnosed With Pancreatic Insulinoma Prior To- And After Surgical Excision

Abstract Disclosure: S.J. Lawless: None. A. McGrath: None. R. Campbell: None. D. O'Keeffe: None. M.J. Bell: None. Insulinomas are rare pancreatic tumours characterised by episodes of hyperinsulinaemic hypoglycaemia. Patients may develop secondary diabetes following surgical intervention for insulinoma. Glycated haemoglobin (HbA1c) is a reliable bio-marker for the diagnosis and prognosis of diabetes. HbA1c is a useful surrogate marker for insulinoma (1). A retrospective analysis of patients diagnosed with insulinoma and attending our service in Galway University Hospital (GUH) was performed. Data was collected using the electronic patient correspondence system to gather information from clinic letters, hospital and GP laboratory results were accessed on the Evolve laboratory system. Diagnostic criteria employed a 72-hour fast with plasma glucose levels of ≤2.2 mmol/L, with a corresponding insulin level ≥18 pmol/L and a c-peptide of <200 pmol/l. We analysed their HbA1c at initial presentation and longitudinally following treatment. There are currently six patients carrying a diagnosis of insulinoma attending our service. All of these patients have had surgical intervention. At diagnosis four of the six patients had a HbA1c taken. One patient was diagnosed prior to HbA1c being routinely available and another patient had initial investigations and management elsewhere. The average HbA1c at time of diagnosis was 27.75 mmol/mol (n=4) (reference range 20 to 42 mmol/mol). All insulinoma patients have their HbA1c monitored yearly as part of ongoing follow-up. HbA1c trends upwards with an average HbA1c 18-24 months post surgical excision of 36.25 mmol/mol (n=4). There is a tendency of increased HbA1c post-operatively with a mean increase in HbA1c of 8.5 mmol/mol over 18-24 months. Three of our six patients have developed diabetes on extended follow-up. The average time to diagnosis post-surgical resection was 5.5 years (n=3). HbA1c is a useful tool for monitoring for secondary diabetes post pancreatic surgery. While admitting our number of patients is low, it is interesting to observe the difference in HbA1c pre- and post-operatively in patients with insulinoma. 1.Vaidakis, Dennis, et al. "Pancreatic insulinoma: current issues and trends." Hepatobiliary & pancreatic diseases international: HBPD INT 9.3 (2010): 234-241. Presentation: Saturday, June 17, 2023

Aggressive Adult Pancreatoblastoma with Early Recurrence: A Case Report

Background: Pancreatoblastoma (PB) is a rare malignant epithelial tumor of the pancreas, mainly occurring in pediatric population. Pancreatoblastoma of the adult is extremely rare and usually shows a more aggressive biological behavior and a worse prognosis. Case Presentation: The patient was a 54-year-old man admitted for abdominal pain and weight loss. A computed tomography (CT) scan showed a 12 cm heterogeneous hypoattenuating mass in the pancreatic head. An endoscopic ultrasound-guided biopsy suggested the diagnosis of pancreatoblastoma (PB). The patient underwent a pancreaticoduodenectomy (PD) combined with limited liver resections for intraoperative finding of multiple liver metastasis. Pathological findings confirmed the diagnosis of PB metastatic to the liver. The tumor recurred in the liver 5 months after surgery and the patient succumbed due to tumor dissemination 8 months after initial diagnosis. Conclusion: Adult pancreatoblastoma is a rare pancreatic neoplasm with malignant behavior. The aim of this manuscript is to report our experience with pancreatoblastoma in the adult and to contribute improving knowledge about the clinical behavior of this rare and aggressive malignancy.

Dual role of autotaxin as novel biomarker and therapeutic target in pancreatic neuroendocrine neoplasms.

Pancreatic neuroendocrine neoplasms (panNENs) are rare pancreatic neoplasms, and descriptions of treatment remain limited. Autotaxin (ATX) is a secreted autocrine motility factor involved in the production of lysophosphatidic acid (LPA), a lipid mediator that promotes the progression of various cancers. The aim of this study was to clarify the importance of the ATX-LPA axis in panNENs and to confirm its contribution to panNEN progression using clinical data, cell lines, and a mouse model. Serum ATX level was higher in patients with panNEN than in patients with other pancreatic diseases (chronic pancreatitis, pancreatic ductal adenocarcinoma [PDAC], intraductal papillary mucinous neoplasm, autoimmune pancreatitis) and healthy controls, and 61% of clinical specimens stained strongly for ATX. In a case we encountered, serum ATX level fluctuated with disease progression. An in vitro study showed higher ATX mRNA expression in panNEN cell lines than in PDAC cell lines. Cell proliferation and migration in panNEN cell lines were stimulated via the ATX-LPA axis and suppressed by RNA interference or inhibitors. An in vivo study showed that intraperitoneal injection of GLPG1690, an ATX inhibitor, suppressed tumor progression in a xenograft model. These findings revealed that ATX expression is significantly elevated in panNEN and is related to the progression of panNEN. We showed the potential of ATX as a novel biomarker and therapeutic target.

Recurrent Hypoglycemia: Endoscopic Ultrasound to the Rescue

Insulinoma is a rare pancreatic neuroendocrine tumor with an incidence of 4 per million. Ectopic insulinomas are even rarer and comprise 1-2% of these cases. In cases which have established endogenous hyperinsulinemic hypoglycemia, a high-index of suspicion must be maintained since conventional tests like Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) may miss these tumors. Endoscopic ultrasound can be utilised in localisation as it is more sensitive and specific compared to CT or MRI with an added applicability in obtaining a biopsy. However, operator skill and experience play a crucial role in identifying extra-pancreatic insulinomas.

Clinicopathological Features of Insulinoma: A Single Tertiary Center Experience.

Insulinoma is a rare pancreatic neuroendocrine tumor with an incidence of 1-4 cases per million. Here we present our 10years of experience in 13 cases of insulinoma. We retrospectively reviewed all insulinoma patients diagnosed and treated between 2012 and 2022. Clinical and pathological features, diagnostic methods, and follow-up results of insulinoma patients were discussed. A total of 13 patients were included in this study (7 men, and 6 women). The mean age at the time of diagnosis was 58 (36.5-70.5) years. There is only one patient diagnosed with MEN-1 syndrome. The mean time from the onset of symptoms to the diagnosis was 15 (7-27.5) months. In the prolonged fasting test, symptomatic hypoglycemia occurred in all patients within 48h. The median size of lesions was 15 (12-24) mm, and 46.2% of these lesions were isolated in the pancreatic tail. Ga-68 DOTATATE PET/CT detected lesions with 100% accuracy. Three patients met the criteria for malignant insulinoma. Octreotide LAR was given to 1 patient with metastatic disease and 1 patient who did not accept surgery. The metastatic patient received 8 cycles of Lu treatment and died after 51months of follow-up. The diagnosis of insulinoma can be challenging. The 48-h fasting test period provided sufficient information for the diagnosis of insulinoma. Ga-68 DOTATATE PET/CT may be an alternative in cases where cross-sectional imaging cannot localize the pancreatic lesion.

Solid Pseudopapillary Neoplasm of the Pancreas: A Single-Center Experience of a Rare Neoplasm.

Solid pseudopapillary neoplasm (SPN) of the pancreas is an extremely rare pancreatic exocrine tumor. The study aims to report our experience with the SPN of the pancreas. A retrospective analysis of the prospectively maintained database was carried out of all the cases diagnosed and treated as SPN between January 2019 and January 2023. Patient characteristics including age, gender, clinical presentation, laboratory examinations, imaging features, surgical details, and histopathological and immunohistochemistry details were analyzed. During this period, eight cases were diagnosed with SPN. All patients were female with a median age of 25.75 years (range 14-55 years). All cases presented with pain in the abdomen, and four patients had a mass per abdomen. In all the cases, contrast-enhanced computed tomography (CECT) abdomen was done for the diagnosis and had preoperative suspicion of the pseudopapillary tumor. In four cases, the tumor was located in the head region, while in four cases, the tumor was in the body and tail of the pancreas. The median size of the tumor was 12 cm (range 3.5-15 cm). Three cases underwent Whipple's procedure and one patient was unresectable. Two out of four patients with body and tail tumors underwent distal pancreatectomy with splenectomy, one underwent spleen-preserving distal pancreatectomy, and one patient underwent central pancreatectomy. SPN is a rare neoplasm that primarily affects young women. Clinicopathologic and immunohistochemical features are diagnostic. Surgical resection is generally curative with a good long-term outcome.

Abstract #1404146: The Ups and Downs of Diagnosing Insulinoma

Insulinomas are rare neuroendocrine tumors of the pancreas. The diagnosis of an insulinoma may be delayed in the geriatric population, as older individuals often have comorbid conditions making evaluation more difficult. The case described here involves an exceptionally rare presentation of insulinoma in a 78-year-old male with underlying type 2 diabetes mellitus and heart failure. A 78-year-old man with a past medical history of type 2 diabetes, heart failure, and chronic kidney disease presented to the hospital with bilateral lower extremity edema and shortness of breath. He had been hospitalized four times during the previous six months for acute heart failure exacerbations accompanied by recurrent episodes of hypoglycemia. Of note, his diabetes was well-controlled with glimepiride and dapagliflozin only. The patient reported symptomatic hypoglycemia, primarily during fasting episodes, with nadir serum glucose values between 40 and 50 mg/dL. During hospitalizations, total insulin (range 22-68 uU/mL), and C peptide (range 6.9-16.4 ng/mL) concentrations were inappropriately elevated when glucose was low, indicative of endogenous hyperinsulinemia. However, this hypoglycemia was thought to be secondary to recent sulfonylurea use in the setting of poor diet and acute renal insufficiency related to heart failure. Both glimepiride and dapagliflozin were held, though he inadvertently continued to take glimepiride until his fourth hospitalization. During his fourth admission, the patient continued to have symptomatic hypoglycemia. As his sulfonylurea screen was negative, he underwent an Octreoscan that revealed radiotracer uptake in the distal pancreas. An endoscopic ultrasound with biopsy revealed a well-differentiated neuroendocrine tumor of the pancreas. His heart failure made agents such as diazoxide, verapamil, and phenytoin undesirable, and he was discharged on subcutaneous octreotide three times daily with a plan to follow up in the surgery clinic. The presentation of insulinomas in the geriatric population can be variable and nonspecific, increasing the risk of misdiagnosis or delay of diagnosis. Missing the diagnosis can lead to increased morbidity and mortality via cognitive impairment and falls. Our patient experienced a delay in diagnosis of insulinoma of over one year despite satisfying the criteria of Whipple’s triad during his first admission. The patient had been asked to stop all anti-diabetic medications during his third admission. However, he misunderstood and continued glimepiride. Further, his acute renal insufficiency, heart failure, and decreased appetite provided alternative causes for his hypoglycemia. Insulinomas are extremely rare pancreatic neuroendocrine tumors that typically present in patients between 40 and 60 years of age. However, there have been reports of these rare tumors in older individuals, who often have comorbid conditions making their diagnosis more difficult. This case report highlights the importance of including insulinoma as a cause of persistent endogenous hypoglycemia among the geriatric population.

Comments on and Illustrations of the EFSUMB CEUS Guidelines: Transabdominal and Endoscopic Ultrasound Features of Intrapancreatic Metastases and the Role of Multiparametric Imaging and EUS-Guided Sampling in Rare Pancreatic Tumors.

A definite pathologic diagnosis of intrapancreatic metastasis is crucial for the management decision, i.e., curative or palliative surgery versus chemotherapy or conservative/palliative therapy. This review focuses on the appearance of intrapancreatic metastases on native and contrast-enhanced transabdominal ultrasound and endoscopic ultrasound. Differences and similarities in relation to the primary tumor, and the differential diagnosis from pancreatic carcinoma and neuroendocrine neoplasms are described. The frequency of intrapancreatic metastases in autopsy studies and surgical resection studies will be discussed. Further emphasis is placed on endoscopic ultrasound-guided sampling to confirm the diagnosis.

Intraductal papillary mucinous neoplasm originating from a jejunal heterotopic pancreas: A case report

Intraductal papillary mucinous neoplasm (IPMN) is a rare pancreatic tumor and has the potential to become malignant. Surgery is the most effective treatment at present, but there is no consensus on the site of resection. Heterotopic pancreas occurs in the gastrointestinal tract, especially the stomach and duodenum but is asymptomatic and rare. We report a case of ectopic pancreas with IPMN located in the jejunum. A 56-year-old male patient suffered from severe pain, nausea and vomiting due to a traffic accident and sought emergency treatment at our hospital. Contrast-enhanced computed tomography of the whole abdomen suggested splenic congestion, which was considered to be splenic rupture. Emergency laparotomy was performed, and the ruptured spleen was removed during the operation. Unexpectedly, a cauliflower-like mass of about 2.5 cm × 2.5 cm in size was incidentally found about 80 cm from the ligament of Treitz during the operation. A partial small bowel resection was performed, and postoperative pathology confirmed the small bowel mass as heterotopic pancreas with low-grade IPMN. Ectopic pancreas occurs in the jejunum and is pathologically confirmed as IPMN after surgical resection.

Rare Non-Neuroendocrine Pancreatic Tumours

The most common tumour of the pancreas is ductal adenocarcinoma (PDAC). It remains one of the most lethal non-neuroendocrine solid tumours despite the use of a multi-approach strategy. Other, less-common neoplasms, which are responsible for 15% of pancreatic lesions, differ in treatment and prognosis. Due to the low incidence rate, there is a lack of information about the rarest pancreatic tumours. In this review, we described six rare pancreatic tumours: intraductal papillary mucinous neoplasm (IPMN), mucinous cystadenoma (MCN), serous cystic neoplasm (SCN), acinar cell carcinoma (ACC), solid pseudopapillary neoplasm (SPN) and pancreatoblastoma (PB). We distinguished their epidemiology, clinical and gross features, covered the newest reports about courses of treatment and systematised differential diagnoses. Although the most common pancreatic tumour, PDAC, has the highest malignant potential, it is still essential to properly classify and differentiate less-common lesions. It is vital to continue the search for new biomarkers, genetic mutations and the development of more specific biochemical tests for determining malignancy in rare pancreatic neoplasms.

Solid Pseudopapillary Epithelial Neoplasm of the Pancreas: A Rare Entity with Diagnostic Dilemma

The solid pseudopapillary epithelial neoplasm (SPEN) of the pancreas is a relatively uncommon entity. The aim of the present study was to summarize our experiences with regard to diagnostic dilemma, surgery, postoperative follow-up, and management. This retrospective data were collected during the period from January 1, 2018 to December 31, 2020. A total of four patients (three females and one male) were identified within an age range of 13 to 25 years. All the patients were presented with nonspecific symptoms such as abdomen lumps, swelling in the abdomen, and abdominal pain. To reach a definite diagnosis, imaging studies were conducted along with endoscopic ultrasound fine-needle aspiration (EUS-FNA) and biopsy. After confirmation of SPEN on biopsy, all the patients underwent surgery without any complications. Patients are on follow-up, and to date, no metastasis has been detected. SPEN is a rare pancreatic tumor with unusual pathological features leading to a diagnostic dilemma. The pathologist should be familiar with SPEN and its salient histological characteristics that differentiate it from other look-alike pancreatic tumors and can help in timely surgery and management.

A rare pancreatic tumor mimicking chronic calcified pancreatitis.

A 48-year-old woman was admitted for severe upper abdominal pain, with impressive dilation and multiple high-density stones in the main pancreatic duct (PD). The patient was diagnosed with “chronic pancreatitis” and a therapeutic endoscopic retrograde cholangiopancreatography (ERCP) was planned.

The Role of MRI in the Diagnosis of Solid Pseudopapillary Neoplasm of the Pancreas and Its Mimickers: A Case-Based Review with Emphasis on Differential Diagnosis.

Solid pseudopapillary neoplasm (SPN) is rare pancreatic tumor occurring most commonly in young females. The typical imaging appearance of SPN is of well-defined, encapsulated, and large heterogeneous tumors, consisting of solid and cystic components due to various degrees of intralesional hemorrhage and necrosis. However, atypical imaging presentation in the form of small solid tumors or uniformly cystic lesions might also be seen, which can be explained by specific pathological characteristics. Other imaging features such as a round shape, the absence of main pancreatic duct dilatation, and slow growth, in combination with vague symptoms, favor the diagnosis of SPNs. Nevertheless, the radiological findings of SPN might overlap with other solid and cystic pancreatic neoplasms, such as neuroendocrine tumors, serous and mucinous neoplasms, and even small pancreatic adenocarcinomas. In addition, a few benign non-tumorous conditions including walled-of-necrosis, and intrapancreatic accessory spleen may also pose diagnostic dilemmas simulating SPNs on imaging studies. The aim of this manuscript is to provide a comprehensive overview of the typical and atypical imaging features of SPNs and to describe useful tips for differential diagnosis with its potential mimickers.

A rare case of pancreatic acinar cell carcinoma presenting a submucosal tumor.

A 66-year-old man, who underwent distal gastrectomy with Billroth I reconstruction for gastric cancer, regularly underwent upper endoscopy as a routine examination. Unlike 1 year earlier [Figure 1a], a submucosal tumor-like lesion was identified near the minor papilla [Figure 1b], but the opening of the minor papilla could not be confirmed. Computed tomography revealed a mass (26 mm × 10 mm) protruding from the duodenal wall into the duodenal lumen [Figure 2] without pancreatic duct dilation. EUS using a linear array echoendoscope showed that the hypoechoic and smooth-marginal mass adjacent to the pancreatic head [Figure 3a] and the accessory pancreatic duct could not be recognized. EUS using a miniature probe showed that the mass was mainly located in the muscularis propria of the duodenal wall [Figure 3b]. The initial diagnosis was a duodenal gastrointestinal stromal tumor; however, EUS-guided fine-needle biopsy of the mass revealed suspicious pancreatic acinar cell carcinoma (PACC). A pancreaticoduodenectomy was performed. Macroscopically, a gray-white mass with a 25-mm maximum diameter was found in the duodenal submucosa on the cut surface [Figure 4a]. The boundary between the mass and the pancreatic parenchyma was unclear. Predominant growth of the tumor was observed within the accessory pancreatic duct by loupe image [Figure 4b]. No invasive growth or cystic formation was found. The tumor cells having irregular, hyperchromatic nuclei and eosinophilic cytoplasm proliferated mainly in an acinar or tubular pattern [Figure 4c]. The neoplastic cells were diffusely positive for anti-trypsin [Figure 4d] and bcl-10, whereas they were negative for a neuroendocrine marker, chromogranin or synaptophysin. Finally, the pathological diagnosis was a PACC at stage TisN0M0.Figure 1: (a) Endoscopic image showing no abnormality of the duodenal wall and minor papilla 1 year ago. (b) Endoscopic image showing a submucosal tumor-like lesion near the original minor papillaFigure 2: Contrast-enhanced computed tomography showing a mass (arrow) protruding from the duodenal wall into the duodenal lumen located in contact with the pancreatic headFigure 3: (a) EUS using a linear array echoendoscope showing a hypoechoic and smooth-marginated mass outside the pancreatic head. (b) EUS using a miniature probe showing the mass mainly located in the muscularis propria of the duodenal wallFigure 4: (a) Gross examination of resected specimen revealed a gray-white, solid lesion mainly occupying the duodenal submucosa on the cut surface. (b) A tumor with intraductal growth was observed by loupe image of histologic specimen (H and E). Normal pancreatic parenchyma (arrow). (c) Tumor cells having irregular, hyperchromatic nuclei and eosinophilic cytoplasm proliferated resembling acini of the pancreas (H and E, × 200). (d) Immunohistochemically, the neoplastic cells were positive for anti-trypsin (×40)PACC is a rare pancreatic tumor,[1] which is typically a solid tumor with expansive growth.[2] A PACC that predominantly grows within the main pancreatic ducts is extremely rare.[3] There has not been any reported case of PACC growing in the accessory pancreatic duct and presenting a submucosal tumor. In this case, there are some hypotheses regarding the specific tumor appearance: PACC originating from (1) pancreatic parenchyma near the accessory pancreatic duct and (2) ectopic pancreas[4] or submucosal pancreatic parenchyma.[5] However, it is a limitation that it was difficult to prove the hypotheses. Authors’ contributions R.S. treated the patient and wrote the manuscript; H.K., H.N., S.H., T.M., K.S., T.Y., H.A., M.K., M.F., T.M., M.F., K.O., E.T., T.U., A.T., and A.I. treated the patient and contributed writing the manuscript; T.T. performed pathological diagnosis and contributed writing the manuscript; all authors approved the final manuscript. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest Masaki Kuwatani is an Editorial Board Member of the journal. This article was subject to the journal’s standard procedures, with peer review handled independently of the editor and his research group.

Single-cell RNA sequencing of solid pseudopapillary neoplasms of the pancreas in children.

Solid pseudopapillary neoplasm (SPN) of the pancreas is a rare pancreatic tumor in children. Its origin remains elusive, along with its pathogenesis. Heterogeneity within SPN has not been previously described. In addition, low malignant but recurrent cases have occasionally been reported. To comprehensively unravel these profiles, single-cell RNA sequencing was performed using surgical specimens. We identified the cell types and suggested the origin of pancreatic endocrine progenitors. The Wnt/β-catenin pathway may be involved in tumorigenesis, while the epithelial-to-mesenchymal transition may be responsible for SPN recurrence. Furthermore, NOV, DCN were nominated as primary and S100A10, MGP as recurrent SPN marker genes, respectively. Our results provide insight into the pathogenesis of SPN.