Serous Neoplasms of the Pancreas: A Comprehensive Review

INSM1 is a useful neuroendocrine marker to differentiate pancreatic serous cystadenoma from pancreatic well-differentiated neuroendocrine tumors in cytology and surgical specimens

INTRODUCTION

Differentiating pancreatic serous cystadenoma (SCA) from well-differentiated neuroendocrine tumors (WDNETs) based on histomorphology is critical yet challenging, particularly in small biopsy samples. Our study aimed to examine the expression profile of INSM1 in cytologic and surgical resection specimens from pancreatic SCA to evaluate its potential as a discriminative marker against pancreatic WDNET.

METHODS

We characterized INSM1 immunohistochemistry in 34 patients with pancreatic SCA, comprising 23 surgical resections and 11 cytology specimens. As a control, we used 28 cytology specimens from pancreatic WDNET. Clinical information was retrieved through a review of electronic medical records.

RESULTS

All 11 pancreatic SCA cytology specimens and 15 of 23 pancreatic SCA surgical resections exhibited absent INSM1 immunostaining. Each of the remaining eight surgical resection specimens demonstrated 1 % immunoreactivity. In contrast, 27 out of 28 (96 %) pancreatic WDNET cytology specimens were positive for INSM1 immunostaining, with a median immunoreactivity of 90 % and a range of 30-90 %. Overall, INSM1 immunostains perform similarly to chromogranin and synaptophysin in pancreatic SCA.

CONCLUSIONS

The results indicate that INSM1 immunohistochemistry staining may serve as a useful neuroendocrine marker to differentiate pancreatic SCA from pancreatic WDNET in clinical practice. To our knowledge, this represents the first large-scale study to evaluate INSM1 immunostaining in surgical and cytology specimens from pancreatic SCA.

Imaging of pancreatic serous cystadenoma and common imitators

Pancreatic cystic neoplasms are lesions comprised of cystic components that show different biological behaviors, epidemiology, clinical manifestations, imaging features, and malignant potential and management. Benign cystic neoplasms include serous cystic neoplasms (SCAs). Other pancreatic cystic lesions have malignant potential, such as intraductal papillary mucinous neoplasms and mucinous cystic neoplasms. SCAs can be divided into microcystic (classic appearance), honeycomb, oligocystic/macrocystic, and solid patterns based on imaging appearance. They are usually solitary but may be multiple in von Hippel-Lindau disease, which may depict disseminated involvement. The variable appearances of SCAs can mimic other types of pancreatic cystic lesions, and cross-sectional imaging plays an important role in their differential diagnosis. Endoscopic ultrasonography has helped in improving diagnostic accuracy of pancreatic cystic lesions by guiding tissue sampling (biopsy) or cyst fluid analysis. Immunohistochemistry and newer techniques such as radiomics have shown improved performance for preoperatively discriminating SCAs and their mimickers.

A Serous Cystic Tumor and a Pancreatic Neuroendocrine Tumor in the Same Patient: A Case Report and Literature Review

A serous cystic tumor is a rare entity that has a benign course. Its imaging characteristics, such as the presence of multiple cysts with or without nodular enhancement, can simulate other cystic or solid lesions of the pancreas. Identification of the enhancing scar with punctate calcifications on computed tomography (CT) or magnetic resonance imaging (MRI) may be a distinctive finding suggesting this diagnosis. Neuroendocrine tumors of the pancreas are a different and also rare entity. In images, they have early arterial enhancement. In MRI, they are hyperintense on T2 and hypointense on T1, with avid contrast enhancement. A case of a patient with two focal lesions in the pancreas is presented and the importance of integrating clinical findings, semiology in diagnostic images and, if applicable, the histopathological result for the optimal management of pancreatic tumors is illustrated, highlighting the crucial role of a radiologist in this process.

Contrast-enhanced ultrasound (CEUS) and shear wave elastography (SWE) features for characterizing serous microcystic adenomas (SMAs): In comparison to pancreatic neuroendocrine tumors (pNETs)

Objectives

Serous microcystic adenoma (SMA), a primary benign pancreatic tumor which can be clinically followed-up instead of undergoing surgery, are sometimes mis-distinguished as pancreatic neuroendocrine tumor (pNET) in regular preoperative imaging examinations. This study aimed to analyze preoperative contrast-enhanced ultrasound (CEUS) and shear wave elastography (SWE) features of SMAs in comparison to pNETs.

Material and methods

In this retrospective study, patients with imaging-diagnosed pancreatic lesions were screened between October 2020 to October 2022 (ethical approval No. B2020-309R). Performing by a Siemens Sequoia (Siemens Medical Solutions, Mountain View, CA, USA) equipped with a 5C-1 curved array transducer (3.0-4.5 MHz), CEUS examination was conducted to observe the microvascular perfusion patterns of pancreatic lesions in arterial phase, venous/late phases (VLP) using SonoVue® (Bracco Imaging Spa, Milan, Italy) as the contrast agent. Virtual touch tissue imaging and quantification (VTIQ) - SWE was used to measure the shear wave velocity (SWV, m/s) value to represent the quantitative stiffness of pancreatic lesions. Multivariate logistic regression was performed to analyze potential ultrasound and clinical features in discriminating SMAs and pNETs.

Results

Finally, 30 SMA and 40 pNET patients were included. All pancreatic lesions were pathologically proven via biopsy or surgery. During the arterial phase of CEUS, most SMAs and pNETs showed iso- or hyperenhancement (29/30, 97 % and 31/40, 78 %), with a specific early honeycomb enhancement pattern appeared in 14/30 (47 %) SMA lesions. During the VLP, while most of the SMA lesions remained iso- or hyperenhancement (25/30, 83 %), nearly half of the pNET lesions revealed an attenuated hypoenhancement (17/40, 43 %). The proportion of hypoenhancement pattern during the VLP of CEUS differed significantly between SMAs and pNETs (P = 0.021). The measured SWV value of SMAs was significantly higher than pNETs (2.04 ± 0.70 m/s versus 1.42 ± 0.44 m/s, P = 0.002). Taking a SWV value > 1.83 m/s as a cutoff in differentiating SMAs and pNETs, the area under the receiver operating characteristic curve (AUROC) was 0.825, with sensitivity, specificity and likelihood ratio (+) of 85.71 %, 72.73 % and 3.143, respectively. Multivariate logistic regression revealed that SWV value (m/s) of the pancreatic lesion was an independent variable in discriminating SMA and pNET.

Conclusion

By comprehensively evaluating CEUS patterns and SWE features, SMA and pNET may be well differentiated before the operation. While SMA typically presents as harder lesion in VTIQ-SWE, exhibiting a specific honeycomb hyperenhancement pattern during the arterial phase of CEUS, pNET is characterized by relative softness, occasionally displaying a wash-out pattern during the VLP of CEUS.

Pax8 as a useful adjunct marker to differentiate pancreatic serous cystadenoma from clear cell renal cell carcinoma in both cytologic and surgical specimens

BACKGROUND

Histomorphological differentiation between pancreatic serous cystadenoma (SCA) and clear cell renal cell carcinoma (RCC) can be challenging. We aimed to study Paired box 8 protein (Pax8) expression profile in cytologic and surgical specimens with pancreatic SCA to assess its utility as a differentiating marker from clear cell RCC.

METHODS

We characterized Pax8 immunohistochemistry in 33 patients with pancreatic SCA (23 surgical resections and 10 cytology specimens). Nine cytology specimens from metastatic clear cell RCC involving pancreas were used as control tissue. Electronic medical records were reviewed to retrieve clinical information.

RESULTS

All 10 pancreatic SCA cytology specimens, and 16 of 23 pancreatic SCA surgical resections showed absent Pax8 immunostaining, while the remaining 7 surgical resection specimens showed 1%-2% immunoreactivities. Islet and lymphoid cells adjacent to the pancreatic SCA expressed Pax8. In contrast, the proportion of Pax8 immunoreactivity ranged from 50 to 90% (average of 76%) in nine cases of metastatic clear cell RCC involving pancreas. Using a 5% immunoreactivity cutoff, all cases of pancreatic SCA are interpreted as negative for Pax8 immunostains while all cases of metastatic clear cell RCC involving pancreas are interpreted as positive for Pax8 immunostains.

CONCLUSIONS

These results suggest that Pax8 immunohistochemistry staining can be a useful adjunct marker to differentiate pancreatic SCA from clear cell RCC in clinical practice. To the best of our knowledge, this is the first large-scale study of Pax8 immunostaining on surgical and cytology specimens with pancreatic SCA.

A rare case of pancreatic macrocystic serous cystadenoma in an adolescent: a case report and literature review

While serous cystadenomas of the pancreas usually consist of small cysts, one rare variant has been reported to be composed of macrocysts. Herein, we present the case of the youngest patient with macrocystic serous cystadenoma (MSC) to be reported in the literature. The patient was a 17-year-old girl who presented with the major symptoms of a palpable abdominal mass accompanied by epigastric pain and vomiting for several months. A potential malignancy could not be excluded on the basis of imaging studies, which showed a large macrocystic pancreatic tumor that was 7 cm in diameter. Owing to the patient's symptoms, after diagnosing the mass as a pancreatic cystic tumor with potential malignancy and large tumor size, surgical intervention was arranged. Pathological analysis of the biopsy sample suggested MSC. By reviewing the literature, we found several unique characters of MSCs that cause them to be frequently misdiagnosed as potential malignancies. Additionally, the age of MSC occurrence was found to be lower than of general serous cystadenomas. The potential of MSC should be kept in mind by clinicians when diagnosing young people with pancreatic macrocystic lesions.

Cystic Neoplasms of the Pancreas: Differential Diagnosis and Radiology Correlation

Although the probability of pancreatic cystic neoplasms (PCNs) being detected is raising year by year, their differential diagnosis and individualized treatment are still a challenge in clinical work. PCNs are tumors containing cystic components with different biological behaviors, and their clinical manifestations, epidemiology, imaging features, and malignant risks are different. Some are benign [e.g., serous cystic neoplasms (SCNs)], with a barely possible that turning into malignant, while others display a low or higher malignant risk [e.g., solid pseudopapillary neoplasms (SPNs), intraductal papillary mucinous neoplasms (IPMNs), and mucinous cystic neoplasms (MCNs)]. PCN management should concentrate on preventing the progression of malignant tumors while preventing complications caused by unnecessary surgical intervention. Clinically, various advanced imaging equipment are usually combined to obtain a more reliable preoperative diagnosis. The challenge for clinicians and radiologists is how to accurately diagnose PCNs before surgery so that corresponding surgical methods and follow-up strategies can be developed or not, as appropriate. The objective of this review is to sum up the clinical features, imaging findings and management of the most common PCNs according to the classic literature and latest guidelines.

Molecular alterations in pancreatic tumors

Genetic alterations in pancreatic tumors can usually be classified in: (1) Mutational activation of oncogenes; (2) Inactivation of tumor suppressor genes; and (3) Inactivation of genome maintenance genes controlling the repair of DNA damage. Endoscopic ultrasound-guided fine-needle aspiration has improved pre-operative diagnosis, but the management of patients with a pancreatic lesion is still challenging. Molecular testing could help mainly in solving these “inconclusive” specimens. The introduction of multi-gene analysis approaches, such as next-generation sequencing, has provided a lot of useful information on the molecular characterization of pancreatic tumors. Different types of pancreatic tumors (e.g., pancreatic ductal adenocarcinomas, intraductal papillary mucinous neoplasms, solid pseudopapillary tumors) are characterized by specific molecular alterations. The aim of this review is to summarize the main molecular alterations found in pancreatic tumors.

The Elusive Appearance of Hyperenhancing Solid Serous Cystadenoma of the Pancreas—Radio-Pathological Correlation

Serous cystadenomas account for ~10 to 29% of pancreatic cystic tumors. Solid serous cystadenoma (SSCA) is a rare variant, first described in 1996, with imaging characteristics different from the classical serous cystadenoma of the pancreas and can cause a diagnostic dilemma due to its resemblance to other solid tumors of the pancreas. To the best of our knowledge, only 22 cases of SSCA of pancreas have been reported till date.

A 50-year-old female patient underwent contrast-enhanced computed tomography (CECT) of the abdomen for a hypoechoic lesion detected in the body of the pancreas during ultrasound (US) examination. Due to the hyperenhancement of the well-circumscribed lesion in the arterial phase, a provisional diagnosis of neuroendocrine tumor was considered. Gallium 68-labeled somatostatin-analog (Ga 68-DOTANOC) positron emission tomography CT scan did not show any uptake within the lesion and endoscopic US (EUS)-guided fine-needle aspiration cytology (FNAC) was also inconclusive. She underwent laparotomy and the lesion was enucleated and it was proven to be a serous microcystadenoma on postoperative histopathologic examination.

A diagnosis of SSCA should be considered for solid-appearing pancreatic lesions with characteristic CECT features such as arterial phase hyperenhancement, and immediate washout, along with negative results on DOTANOC scan and EUS-guided FNAC. Malignant transformation of SSCA has not been reported till date, and hence these can be safely followed up, instead of invasive surgery.

Management Algorithms for Pancreatic Cystic Neoplasms: The Surgeon's Perspective

CONTEXT.—

The detection of pancreatic cystic neoplasms (PCNs) has increased owing to the advancement and widespread use of imaging modalities, resulting in differences between past and current management methods for PCNs, including intraductal papillary mucinous neoplasms (IPMNs). Therefore, clinicians should accurately diagnose and determine appropriate treatment strategies. However, previously published treatment guidelines for IPMNs present different indications for treatment.

OBJECTIVE.—

To review the current status of PCNs, including epidemiologic change, malignancy risk, and factors for treatment, and to provide the optimal management algorithms for PCNs, including IPMNs, from the clinician's point of view.

DATA SOURCES.—

Literature review of published studies and the authors' own work.

CONCLUSIONS.—

The treatment of PCNs relies on the type of cyst that is present or suspected. Serous cystic neoplasms are usually benign, and observation is sufficient. However, surgical treatment is required for mucinous cystic neoplasms, and malignancy risk differs according to lesion size. Solid pseudopapillary neoplasms also require surgery. The detection of small IPMNs has been increasing, and most branch duct-type IPMNs are dormant. However, cysts 3 cm or larger or growing branch duct-type IPMNs must be carefully monitored because of the increasing risk of malignancy. Therefore, surveillance strategies should be different according to the size of the lesions. A tailored approach is needed for selecting surgery or surveillance, considering the malignancy potential of the lesion and patient-associated factors such as operative risks and life expectancy. Nomograms are valuable tools for selecting treatment methods as a customized approach for IPMNs.

Serous Microcystic Cystadenocarcinoma of the Pancreas with Synchronous Liver Metastases: Clinical Characteristics and Management

Serous cystadenocarcinoma of the pancreas is a rare but well-established entity. The origin and evolution of this disorder remain unclear, but even metastatic cases have an excellent prognosis. These tumors are very similar to benign serous cystic neoplasms (SCNs) of the pancreas, except that they tend to be larger, are locally invasive, and present distant metastasis. The most frequent local invasion is adjacent vessels, spleen, stomach, and duodenum. The most common site of distant metastasis is the liver. Diagnosis via imaging as well as pathology examination may be misguided due to atypical characteristics of the tumor. In fact, in some, the diagnosis of malignancy was established only after metastases were detected. We present a 60-year-old female patient with malignant serous microcystic cystadenocarcinoma of the pancreas and liver metastasis that was initially misdiagnosed as a metastatic renal cell carcinoma. The patient underwent tumor resection and liver metastasectomy and she is currently doing well after three years of follow-up, with no tumor recurrence or new metastatic liver nodules based on imaging findings.

Elevating pancreatic cystic lesion stratification: Current and future pancreatic cancer biomarker(s)

Pancreatic ductal adenocarcinoma (PDAC) is an incredibly deadly disease with a 5-year survival rate of 9%. The presence of pancreatic cystic lesions (PCLs) confers an increased likelihood of future pancreatic cancer in patients placing them in a high-risk category. Discerning concurrent malignancy and risk of future PCL progression to cancer must be carefully and accurately determined to improve survival outcomes and avoid unnecessary morbidity of pancreatic resection. Unfortunately, current image-based guidelines are inadequate to distinguish benign from malignant lesions. There continues to be a need for accurate molecular and imaging biomarker(s) capable of identifying malignant PCLs and predicting the malignant potential of PCLs to enable risk stratification and effective intervention management. This review provides an update on the current status of biomarkers from pancreatic cystic fluid, pancreatic juice, and seromic molecular analyses and discusses the potential of radiomics for differentiating PCLs harboring cancer from those that do not.

Cystic Lesions of the Pancreas: Differential Diagnosis and Cytologic-Histologic Correlation

CONTEXT.—

Pancreatic cystic lesions (PCLs) are very common, and their detection is increasing with the advances in imaging techniques. Because of the major implications for management, distinguishing between neoplastic and nonneoplastic PCLs is critical. Neoplastic cysts with potential to progress into cancer include mucinous PCLs (intraductal papillary mucinous neoplasms and mucinous cystic neoplasms) and nonmucinous cysts (solid pseudopapillary tumors, serous cystic neoplasms, and neuroendocrine tumors with cystic degeneration). Nonneoplastic cysts with no risk of malignant transformation include pseudocysts, retention cysts, lymphoepithelial cysts, cystic pancreatic lymphangioma, and duplication cyst/ciliated foregut cysts. The role of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) cytology with cyst fluid analysis in the diagnosis of PCLs has evolved during the last decade; however, a definitive diagnosis on cytologic specimens is hampered by the sparse cellularity and can be challenging. EUS-FNA can play an important role to differentiate low-risk from high-risk pancreatic cysts and to distinguish between patients with cysts who need clinical follow-up versus those who require surgery.

OBJECTIVE.—

To provide an integrative approach to diagnose pancreatic cystic lesions using EUS-FNA cytology and cyst fluid analysis, along with clinical, radiologic, histologic, genetic, and molecular characteristics.

DATA SOURCES.—

The review and analysis of the latest literature describing pancreatic cystic lesions.

CONCLUSIONS.—

Accurate diagnosis of PCLs requires a multidisciplinary and multimodal team approach, including the integration of clinical findings, imaging, cytology, cyst fluid analysis, and molecular testing.