“Simple Mucinous Cyst” of the Pancreas: A Clinicopathologic Analysis of 39 Examples of a Diagnostically Challenging Entity Distinct From Intraductal Papillary Mucinous Neoplasms and Mucinous Cystic Neoplasms

Comprehensive Characterization of Intraductal Oncocytic Papillary Neoplasm of the Pancreas: A Systematic and Critical Review

Intraductal oncocytic papillary neoplasm (IOPN) of the pancreas is a recently recognized pancreatic tumor. Here, we aimed to determine its most essential features with the systematic review tool. PubMed, Scopus, and Embase were searched for studies reporting data on pancreatic IOPN. The clinicopathologic, immunohistochemical, and molecular data were extracted and summarized. Then, a comparative analysis of the molecular alterations of IOPN with those of pancreatic ductal adenocarcinoma and intraductal papillary mucinous neoplasm from reference cohorts (including The Cancer Genome Atlas) was conducted. The key findings from 414 IOPNs were as follows: 1) The male-to-female ratio was 1.5:1. Pancreatic head was the most common site (131/237; 55.3%), but a diffuse tumor extension involving more than one pancreatic segment was described in about 1 out of 5 cases (49/237; 20.6%). The mean size was 45.5 mm. An associated invasive carcinoma was present in 50% of cases (168/336). In those cases, most tumors were pT1 or pT2 and pN0 (>80%), and vascular invasion was uncommon (20.6%). Regarding survival, more than 90% of patients were alive after surgical resection. 2) Immunohistochemical and molecular features were as follows. The most commonly expressed mucins were MUC5AC (110/112; 98.2%) and MUC6 (78/84; 92.8%). Compared with pancreatic ductal adenocarcinoma and intraductal papillary mucinous neoplasm, the classic pancreatic drivers KRAS, TP53, CDKN2A, SMAD4, and GNAS were less altered in IOPN (P < .01). Moreover, fusions involving PRKACA or PRKACB gene were detected in all of the 68 cases examined, with PRKACB::ATP1B1 being the most common (27/68 cases; 39.7%). These genomic events emerged as an entity-defining molecular alteration of IOPN (P < .01). Thus, such fusions represent a promising biomarker for diagnostic purposes. Recent evidence also suggests their role in influencing the acquisition of oncocytic morphology. IOPN is a distinct pancreatic neoplasm with specific clinicopathologic and molecular features. Considering the clinical or prognostic implications, its recognition is essential for pathologists and, ultimately, patients' management.

Investigating morphological changes in a simple mucinous cyst during the follow-up period: a case report

A 64-year-old man was referred to our department after a small pancreatic cystic lesion was discovered on computed tomography performed to assess choledocholithiasis. Multiple standard imaging modalities, including endoscopic ultrasound (EUS), failed to reveal pancreatic masses, wall thickening, or mural nodules. Consequently, a benign pancreatic cystic lesion was suspected, and the patient underwent biannual imaging studies including rotating magnetic resonance imaging and EUS. Six years after the initial detection of the pancreatic cyst, wall thickening was observed, leading to a shortened observation period of once every 3 months. After 6.5 years, hypoechoic area surrounding the cyst, which could be interpreted as thickening of the cyst wall was observed, prompting distal pancreatectomy due to the suspicion of malignant disease. The histopathological examination revealed a unilocular mucinous cyst with a single layer of cuboidal cells and low-grade dysplasia. A fibrous proliferation of the polycystic stroma and no ovarian-type stroma was observed. Malignant cells were absent from the cystic epithelium and stroma. The final histopathological diagnosis was a simple mucinous cyst of the pancreatic tail.

Early Cancerous Lesions of the Pancreas and Ampulla: Current Concepts and Challenges

Owing to the increased use of advanced imaging techniques, mass-forming (cystic/intraductal) preinvasive neoplasms are being detected much more frequently and they have rapidly become one of the main focuses of interests in medical field. These neoplasms have very distinctive clinical and radiographic findings, exhibit a spectrum of dysplastic transformation, from low-grade dysplasia to high-grade dysplasia, and may be associated with an invasive carcinoma. Accounting for about 5% to 10% of pancreatic ductal adenocarcinomas, they provide a curable target subset in an otherwise biologically dismal pancreas cancer category.

Pancreatic Cystic Lesions: A Focused Review on Cyst Clinicopathological Features and Advanced Diagnostics

Macroscopic, endomicroscopic, and histologic findings and correlation are an integral part of the diagnostic evaluation of pancreatic cystic lesions (PCLs), as complementing morphologic features seen by different specialties are combined to contribute to a final diagnosis. However, malignancy risk stratification of PCLs with worrisome features can still be challenging even after endoscopic ultrasound guided-fine needle aspiration (EUS-FNA) with cytological evaluation. This review aims to summarize cyst clinicopathological features from the pathologists' perspective, coupled with knowledge from advanced diagnostics-confocal laser endomicroscopy and cyst fluid molecular analysis, to demonstrate the state-of-art risk stratification of PCLs. This review includes illustrative photos of surgical specimens, endomicroscopic and histologic images, and a summary of cyst fluid molecular markers.

Pancreatic Ductal Adenocarcinoma: Molecular Pathology and Predictive Biomarkers

Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis due to the lack of methods or biomarkers for early diagnosis and its resistance to conventional treatment modalities, targeted therapies, and immunotherapies. PDACs are a heterogenous group of malignant epithelial neoplasms with various histomorphological patterns and complex, heterogenous genetic/molecular landscapes. The newly proposed molecular classifications of PDAC based on extensive genomic, transcriptomic, proteomic and epigenetic data have provided significant insights into the molecular heterogeneity and aggressive biology of this deadly disease. Recent studies characterizing the tumor microenvironment (TME) have shed light on the dynamic interplays between the tumor cells and the immunosuppressive TME of PDAC, which is essential to disease progression, as well as its resistance to chemotherapy, newly developed targeted therapy and immunotherapy. There is a critical need for the development of predictive markers that can be clinically utilized to select effective personalized therapies for PDAC patients. In this review, we provide an overview of the histological and molecular heterogeneity and subtypes of PDAC, as well as its precursor lesions, immunosuppressive TME, and currently available predictive molecular markers for patients.

Simple biliary cysts of the liver can be lined by mucinous epithelium

AIMS & METHODS

Simple biliary cysts of the liver are described to be lined by biliary epithelium and may be managed nonsurgically or by deroofing only. By contrast, its important differential diagnosis-mucinous cystic neoplasm (MCN)-is at least focally lined by mucinous epithelium, has malignant potential, and therefore should be resected. Following anecdotal observations in routine diagnostic practice, the following case series was assembled to confirm whether simple biliary cysts of the liver can be lined by mucinous epithelium. Detailed clinicoradiological review, including postoperative follow-up, was also completed to assess whether the presence of mucinous epithelium had any associations, including a risk of hepatobiliary neoplasia.

RESULTS

Histological review of 21 simple biliary cysts received as surgical specimens over a 3- year period confirmed an absence of ovarian-like stroma in all cases. The lining epithelium of seven cysts showed focal supranuclear/apical mucin, as confirmed histochemically. Cysts with mucinous epithelium were generally larger and more often showed histological evidence of previous haemorrhage than cysts without this epithelium. There were no other statistically-significant differences in clinicoradiological features between cysts with and without mucinous epithelium, including at postoperative radiological follow-up.

CONCLUSIONS

Focal mucinous epithelium can be present in at least one-third of surgically-managed, simple biliary cysts of the liver. Such epithelium may be metaplastic and should not be misinterpreted to indicate a diagnosis of MCN but, apart from this, appears to have no clinical significance. Ovarian-like stroma may therefore be the only histological feature that reliably distinguishes MCN from simple biliary cyst.

[Pancreatic cystic space-occupying lesions-Diagnostics, treatment and follow-up care : Current recommendations taking the current German S3 guidelines on pancreatic cancer into account]

Due to their increased detection pancreatic cystic space-occupying lesions are becoming increasingly relevant in the clinical routine and represent a morphologically and biologically heterogeneous and thus clinically demanding as well as potentially (pre)malignant entity. As a result, recommendations for the diagnostics and treatment of pancreatic cystic tumors have now been incorporated into the current German S3 guidelines on pancreatic cancer. The diagnostics of pancreatic cystic space-occupying lesions are based on the following three elements: collection of relevant clinical information, performance of high-resolution imaging procedures and if diagnostic uncertainty persists, puncture diagnostics. Differentiated diagnostics are of essential importance as these represent the basis for an adequate treatment decision. Pancreatic cystic lesions with a relevant risk of malignant transformation, e.g., main duct intraductal papillary mucinous neoplasms (IPMN), followed by mucinous cystic neoplasms (MCN), solid pseudopapillary neoplasms (SPN) and generally pancreatic cystic lesions with risk factors independent of the entity, should be resected, whereas a differentiated and individualized approach is necessary, especially for branch-duct IPMNs. The serous cystic neoplasms (SCN) have no malignant potential and do not require any treatment if they are asymptomatic. Important principles in surgery of pancreatic cancer, such as adequate surgical resection taking oncological standards into account and standardized appropriate histopathological processing of the specimens as well as intraoperative frozen section analysis also play an important role in pancreatic cystic space-occupying lesions. An annual follow-up seems to be meaningful, especially for IPMNs.

Updates in the Diagnosis of Intraductal Neoplasms of the Pancreas

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest types of cancer worldwide. There are many reasons for this dismal prognosis, including the advanced stage at the time of diagnosis and the lack of effective therapeutic approaches. Intraductal papillary mucinous neoplasms (IPMNs) represent detectable and treatable precursor lesions of PDAC. Our understanding of the pathology of IPMNs has evolved over the past few decades, and new advances in diagnostic tools have emerged. The new World Health Organization (WHO) classification scheme now recognizes the previously considered variants of IPMNs, such as intraductal oncocytic papillary neoplasms (IOPNs) and intraductal tubulopapillary neoplasms (ITPNs), as distinct neoplasms. New imaging and molecular diagnostic tests are being developed to recognize these PDAC precursor lesions better. Here, we review the advances in diagnostic tools for IPMNs, IOPNs, and ITPNs, emphasizing the new (5th edition, 2019) WHO classification for pathological diagnosis, molecular markers, new laboratory tests, and imaging tools.

Pancreatic ductal adenocarcinomas associated with intraductal papillary mucinous neoplasms (IPMNs) versus pseudo-IPMNs: relative frequency, clinicopathologic characteristics and differential diagnosis

The literature is highly conflicted on what percentage of pancreatic ductal adenocarcinomas (PDACs) arise in association with intraductal papillary mucinous neoplasms (IPMNs). Some studies have claimed that even small (Sendai-negative) IPMNs frequently lead to PDAC. Recently, more refined pathologic definitions for mucin-lined cysts were provided in consensus manuscripts, but so far there is no systematic analysis regarding the frequency and clinicopathologic characteristics of IPMN-mimickers, i.e., pseudo-IPMNs. In this study, as the first step in establishing frequency, we performed a systematic review of the pathologic findings in 501 consecutive ordinary PDACs, which disclosed that 10% of PDACs had associated cysts ≥1 cm. While 31 (6.2%) of these were IPMN or mucinous cystic neoplasm (MCN), 19 (3.8%) were other cyst types that mimicked IPMN (pseudo-IPMNs) per recent WHO/consensus criteria. As the second step of the study, we performed a comparative clinicopathologic analysis by also including our entire surgical pathology/consultation databases that was comprised of 60 IPMN-associated PDACs, 30 MCN-associated PDACs and 40 pseudo-IPMN-associated PDACs. We found that 84% of true IPMNs were pre-operatively recognized, whereas IPMN was considered in differential diagnosis of 33% of pseudo-IPMNs. Of the 40 pseudo-IPMNs, there were 15 secondary duct ectasias; 6 large-duct-type PDACs; 5 pseudocysts; 5 cystic tumor necrosis; 4 simple mucinous cysts; 3 groove pancreatitis-associated paraduodenal wall cysts; and 2 congenital cysts. Microscopically, pseudo-IPMNs had at least partial mucinous-lining mimicking IPMN but had smaller cystic (mean = 1.9 cm) and larger PDAC (mean = 3.8 cm) components compared to true IPMNs (cyst = 5.7 cm; PDAC = 2.0 cm). In summary, in this pathologically verified analysis that utilized refined criteria, 10% of PDACs were discovered to have cysts ≥1 cm, about two-thirds of which were IPMN/MCN but about one-third were pseudo-IPMNs. True IPMNs underlying the PDACs are often large and are already diagnosed pre-operatively as having an IPMN component, whereas only a third of the pseudo-IPMNs receive IPMN diagnosis by imaging and their cysts are smaller. At the histopathologic level, pseudo-IPMNs are highly prone to misdiagnosis as IPMN, which presumably accounts for much higher association of IPMNs with PDAC as reported in some studies. The subtle but salient characteristics of pseudo-IPMNs elucidated in this study should be combined with careful radiological/clinical correlation in order to exclude pseudo-IPMNs.

A case report of simple mucinous cyst of pancreas detected by rupture

Introduction

Simple mucinous cyst (SMC) of pancreas is a disease defined by the Baltimore Consensus in 2014. Pancreatic mucus-producing neoplasms are considered to be premalignant tumors, but SMC is not considered to have a risk of malignancy or recurrence.

Presentation of case

The case was a woman in her 50s with a chief complaint of abdominal pain. A blood exam showed an increase in the inflammatory response, and a slight increase of Amylase. CT showed a cystic lesion 80 mm in size at tail of the pancreas, and disproportionate fat stranding and ascites around it. We diagnosed peritonitis associated with the rupture of a cystic lesion accompanied by pancreatitis. Abdominal pain was improving, and we decided to proceed with the detailed examination. MRI showed a uniform hyper-intensity on T2WI, and a nodular-like hypo-intensity was observed inside, which was enhanced. During the follow-up, the lesion had gradually grown and re-ruptured. As we could not deny malignancy by image findings, distal pancreatectomy was performed. The intracystic fluid was browny and turbid, and Amylase, CEA and CA19-9 of the cystic fluid were elevated. We diagnosed it SMC by histopathological findings. Currently, she had no recurrence for 1 year.

Discussion

SMC is a type of true cysts, so rupture was rare. However, if the cyst wall becomes weak due to complications such as acute pancreatitis. It is probable that our case had pancreatitis and the cyst wall was weakened.

Conclusion

SMC detected by rupture was very rare, so we report this case.

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SMC of the pancreas in which surgery was required due to rupture was rare case.

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This is unique that it looked like an nodule due to the gathering of cystic walls.

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Non-neoplastic lesions should be considered if nodule grow and shrink over time.

Simple mucinous cyst: another potential cancer precursor in the pancreas? Case report with molecular characterization and systematic review of the literature

Cystic lesions of the pancreas may range from benign to precursors of pancreatic cancer. Simple mucinous cyst (SMC) is larger than 1 cm, has a gastric-type flat mucinous lining, and minimal atypia without ovarian-type stroma. We report a new case of pancreatic SMC, coupling a systematic review of the English literature mainly focused on their clinic-pathological features. We reviewed 103 cases of SMC in adults (73 women), averaging 57 (range, 26–70) years. The SMCs were located in the body-tail region of the pancreas in 60 (58%) cases, presenting as single cystic lesions in 94% of cases; 43% of patients were asymptomatic. A preoperative fine-needle aspiration of the cyst fluid detected amylase and carcinoembryonic antigen positivity in 71% and 76% of cases, respectively. Patients underwent surgery mostly for suspected malignancy; in 83% of cases, a standard pancreatic resection was performed. Mean SMC size was 4.9 (range, 1.5–12.0) cm. Mucins MUC5AC and MUC6 resulted positive in 77% and 81% of cases performed, respectively, whereas MUC2 was negative in all but one patient. The SMC from our institution was characterized by a KRAS somatic mutation. The diagnosis of SMC should be considered when a solitary pancreatic cyst larger than 1 cm is detected in asymptomatic patients. To establish a correct diagnosis, an extensive histologic/immunohistochemical analysis is essential. The presence of a KRAS mutation highlights that SMC may represent another potential pancreatic cancer precursor.

Nonmucinous Cystic Lesions of the Pancreas

CONTEXT.—

Pancreatic cystic lesions are increasingly diagnosed. Among other criteria, they are often distinguished in mucinous versus nonmucinous cysts. Mucinous pancreatic cystic lesions have received increasing attention, especially those known as precursors of pancreatic ductal adenocarcinoma. However, the group of nonmucinous cystic lesions of the pancreas includes numerous entities that may pose a diagnostic challenge. Their accurate diagnosis and classification are crucial for adequate patient management.

OBJECTIVE.—

To review the spectrum of nonmucinous cystic lesions of the pancreas, taking into consideration their epidemiology and typical clinical context, their characteristic gross morphology and histomorphology, as well as their immunohistochemical and molecular profile.

DATA SOURCES.—

Literature was searched and reviewed with MEDLINE via PubMed. Macroscopic and microscopic images were obtained from the archives of the Institute of Pathology, Heinrich Heine University and University Hospital of Duesseldorf, Germany.

CONCLUSIONS.—

Nonmucinous cysts of the pancreas comprise numerous, mostly rare entities displaying different biological behaviors. The most frequent are serous cystic neoplasms, solid-pseudopapillary neoplasms, cystic neuroendocrine tumors, and pancreatitis-associated pseudocysts. Accurate diagnosis can be achieved if characteristic clinical context, histomorphology, and immunoprofile are taken into account.

Simple mucinous cysts of the pancreas have heterogeneous somatic mutations

Simple mucinous cysts of the pancreas have an epithelial lining resembling pancreatic intraepithelial neoplasia but may have a clinical presentation similar to premalignant mucinous neoplasms such as intraductal papillary mucinous neoplasms. Whether the epithelial lining shares genomic alterations with other pancreatic preinvasive neoplasms such as PanIN and intraductal papillary mucinous neoplasm has not been determined. We performed targeted sequencing analysis using a custom-designed MiSeq panel including the full coding regions of 18 pancreatic cancer genes on 13 clinically and pathologically well-characterized simple mucinous cysts. We detected 59 mutations in 15 genes in the cohort, with a median of 4 mutations per cyst (range = 0-16 mutations per cyst). The mutated genes and rate of detected mutations were as follows: KMT2C (MLL3) (62%), KRAS (15%), BRAF (8%), RNF43 (8%), CDKN2a (8%), TP53 (15%), and SMAD4 (8%). No GNAS mutations were detected. Four cases (31%) had no mutations detected. These findings place the majority of simple mucinous cysts of the pancreas in the spectrum of early, low-grade mucinous neoplasia, albeit with a different spectrum of genomic alterations compared with PanIN and intraductal papillary mucinous neoplasm.

Association between macroscopically visible tissue samples and diagnostic accuracy of EUS-guided through-the-needle microforceps biopsy sampling of pancreatic cystic lesions

BACKGROUND AND AIMS

EUS-guided through-the-needle biopsy (TTNB) sampling has been reported to improve diagnostic yield compared with cytology for the evaluation of pancreatic cystic lesions (PCLs). The number of macroscopically visible tissue samples needed to reach an adequate diagnosis is still unknown.

METHODS

This is a retrospective, single-center study on consecutive patients with PCLs with risk features (cyst >3 cm, thickened wall, cyst growth during follow-up, and mural nodules) who underwent TTNB sampling. The capability of differentiating mucinous versus nonmucinous cysts, ability to obtain a cyst-lining epithelium, definition of the grade of dysplasia, and specific diagnosis of cyst histotype were evaluated for 1, 2, or 3 TTNB macroscopically visible specimens.

RESULTS

Sixty-one patients were evaluated. A 100% histologic adequacy was reached by 2 samples (P = .05 versus 1). Compared with cytology, 1 TTNB specimen improved the possibility of defining cyst histotype (P < .0001), whereas 2 specimens increased all 4 diagnostic categories (P < .003). Two specimens also increased diagnostic yield compared with 1 sample (P < .085). The collection of a third sample did not improve the value of any diagnostic categories. A specific diagnosis was reached in 74% of patients with 2 histologic samples. The diagnostic reliability of TTNB sampling compared with surgical histology was 90%, with a 22.9% rate of adverse events.

CONCLUSIONS

Two TTNB macroscopically visible specimens reached 100% histologic adequacy and a specific diagnosis in 74% of patients. The collection of a third specimen did not add any additional information and should be avoided to possibly decrease the risk of adverse events.

[Simple mucinous cyst of the pancreas: Case-report and literature review]

Simple mucinous cyst of the pancreas is an unusual pancreatic cyst, first described by Kosmahl et al. in 2002 with 5 cases. We describe a case of simple mucinous cyst of the pancreas, followed by a literature review. The physiopathology of this cyst is still unclear. It is an epithelial cyst, presenting as unilocular cystic lesion of the pancreatic body or tail, with a clear content, and no communication with the pancreatic duct. Microscopically, the cyst is lined by mucin-producing cells with mild atypia, and contains a fibrous wall without ovarian-like stroma. The prognosis is excellent, as no recurrent disease and progression to malignancy have been described. The non neoplastic origin of this lesion is debated, as cases with KRAS mutation and intra-epithelial neoplastic lesions have been recently reported. It is important to distinguish this lesion from macrocystic serous cystadenoma, mucinous cystic neoplasms and intraductal papillary mucinous neoplasms, by clinical, radiological and pathological features, as the treatment varies from simple surveillance to surgical resection.

Mucinous nonneoplastic cyst of the pancreas: CT and MRI appearances

PURPOSE

The purpose of this retrospective study was to evaluate imaging features of mucinous nonneoplastic cyst (MNNC) of the pancreas.

MATERIALS AND METHODS

Three (0.9%) patients with MNNC of the pancreas were found in 335 surgically resected pancreatic cystic lesions. Three MDCT and two MRI/MRCP studies were retrospectively reviewed.

RESULTS

Three cases of MNNC were found in the pancreatic neck, body, and tail, respectively. All the three cases were multilocular without communication with the main pancreatic duct (MPD), although upstream MPD dilatation was seen in two of the three cases. The signal intensity of the cyst fluid was low on T1-weighted, high on T2-weighted, and low on diffusion-weighted images. Cyst wall was thin in two cases, and the remaining case with obstructive pancreatitis showed visible cyst wall enhancement.

CONCLUSION

Imaging findings of MNNC of the pancreas were nonspecific without communication with the MPD. Cyst wall is typically thin without visible enhancement.

Simple Mucinous Cyst of the Pancreas: Review and Update

CONTEXT

- According to the 2014 Baltimore Consensus Meeting, simple mucinous cysts are defined as macroscopic cysts that are greater than 1 cm in size with gastric-type flat mucinous lining and minimal cytologic atypia without ovarian-type stroma. This lesion has not been widely recognized and has undergone a recent nomenclature change owing to unclear pathogenesis and biologic behavior. Mucinous pancreatic cystic lesions are generally considered precursor lesions of pancreatic adenocarcinoma. However, simple mucinous cysts generally have benign behavior with no recurrence or malignant transformation during short follow-up periods.

OBJECTIVE

- To provide a brief update and summary of the evolving nomenclature and current knowledge of simple mucinous cysts with an overview of their clinical, histopathologic, immunohistochemical, and molecular characteristics, as well as discussion of their differential diagnoses and biological behavior.

DATA SOURCES

- Analysis of the pertinent literature (PubMed) and authors' clinical practice experience based on institutional and consultation materials.

CONCLUSIONS

- Simple mucinous cyst has undergone a nomenclature evolution from mucinous nonneoplastic cyst to the current recommended name of simple mucinous cyst to reflect its unclear pathogenesis and progression. The malignant potential of simple mucinous cyst is still debatable. Recent molecular studies support a neoplastic process, but these cysts generally exhibit benign behavior without recurrence or malignant transformation. Therefore, accurate diagnosis of simple mucinous cysts is critical to distinguish them from other more common and aggressive mucinous pancreatic cysts. Studies with larger cohorts and longer clinical follow-up data are needed to further determine the biologic behavior of this cyst and implications for prognosis.