Lipid-Rich Variant of Pancreatic Endocrine Neoplasms

Unveiling lipid-rich ("clear cell") pancreatic neuroendocrine tumor: A small series of two cases with literature review

This study presents two cases of lipid-rich pancreatic neuroendocrine tumors (PanNETs), a rare variant posing significant diagnostic challenges in fine needle aspiration (FNA) cytology and small biopsies. The first case involves an elderly male with a pancreatic tumor, displaying distinct cytoplasmic vacuoles, while the second case is a middle-aged male present with a pancreatic tail mass exhibiting foamy cytoplasm and eccentric nuclei, infiltrating in the stroma. Both cases did not exhibit typical morphologic features of PanNET but demonstrated cytomorphologic features and infiltrative growth patterns that mimicked adenocarcinoma. Further work-up demonstrated that both tumors were immunoreactive for synaptophysin and chromogranin, and were interpreted as well-differentiated, PanNET, lipid-rich variant. The study highlights the overlapping morphological features between lipid-rich PanNETs and other pancreatic neoplasms and underscores the importance of comprehensive cytological and immunohistochemical analysis for accurately diagnosing this variant, particularly due to the risk of misinterpreting it as pancreatic adenocarcinoma. Recognizing lipid-rich PanNETs is crucial for appropriate clinical management, as their identification can significantly impact treatment decisions and patient outcomes.

Pancreatic PEComa, a not so uncommon neoplasm? Systematic review and therapeutic update

Pancreatic PEComas are extremely rare neoplasms with malignant potential, which mostly affect middle-aged women and are characterized by presenting melanocytic and myogenic markers in immunohistochemical analysis. There are no symptoms or pathognomonic imaging tests, so the diagnosis is established with the analysis of the surgical specimen or the FNA obtained with preoperative endoscopic ultrasound. The mean treatment consists on radical excision, adapting the intervention to the location of the tumor. To date, 34 cases have been described; however, more than 80% of them have been reported in the last decade, which suggests that it is a more frequent pathology than expected. A new case of pancreatic PEComa is reported and a systematic review of the literature is carried out according to the PRISMA guidelines with the aim of divulge this pathology, deepening its knowledge and updating its management.

Cytopathology of solid pancreatic neoplasms: An algorithmic approach to diagnosis

The classification and management of solid pancreatic neoplasms has expanded significantly in recent years because of advances in immunohistochemical markers, molecular diagnostics, and therapeutics. Solid pancreatic masses are subdivided into 1) ill-defined, scirrhous, and stroma-rich (ductal adenocarcinoma) and 2) well circumscribed, cellular, and stroma-poor (including neuroendocrine neoplasms, acinar cell carcinoma, pancreatoblastoma, and solid-pseudopapillary neoplasm). Definitive diagnosis, particularly of stroma-poor, circumscribed tumors, requires the incorporation of radiologic and cytologic findings, along with the judicious use of (broad, but limited) immunohistochemical panels (pancytokeratin and neuroendocrine [synaptophysin], acinar [trypsin], and solid-pseudopapillary neoplasm [β-catenin] markers), along with unstained slides. Depending on the initial results, immunohistochemical panels should be expanded to include more confirmatory (acinar and neuroendocrine) markers. This ensures that adequate material is available for definitive diagnosis/subclassification and, in some cases, grading, and/or molecular studies, particularly of grade 3 neuroendocrine neoplasms and mixed-lineage tumors. The objective of this review is to expand the understanding of the cytomorphology of solid pancreatic neoplasms using an integrated, multidisciplinary approach in their diagnosis. Knowledge and understanding of recent updates in the classification of solid pancreatic neoplasms ensures that cytopathologists appropriately triage specimens, judiciously use and interpret ancillary studies, and incorporate these results in reporting.

Current Pathology Model of Pancreatic Cancer

Pancreatic cancer (PC) is one of the most aggressive and lethal malignant neoplasms, ranking in seventh place in the world in terms of the incidence of death, with overall 5-year survival rates still below 10%. The knowledge about PC pathomechanisms is rapidly expanding. Daily reports reveal new aspects of tumor biology, including its molecular and morphological heterogeneity, explain complicated "cross-talk" that happens between the cancer cells and tumor stroma, or the nature of the PC-associated neural remodeling (PANR). Staying up-to-date is hard and crucial at the same time. In this review, we are focusing on a comprehensive summary of PC aspects that are important in pathologic reporting, impact patients' outcomes, and bring meaningful information for clinicians. Finally, we show promising new trends in diagnostic technologies that might bring a difference in PC early diagnosis.

Reconsideration of Clinicopathologic Prognostic Factors in Pancreatic Neuroendocrine Tumors for Better Determination of Adverse Prognosis

The question of how successful we are in predicting pancreatic neuroendocrine tumors (panNET) with poor prognosis has not been fully answered yet. The aim of this study was to investigate the effects of clinicopathological features on prognosis and to determine their validity in prediction of prognosis and whether a better prognostic classification can be made. Fifty-six patients who underwent pancreatic resection for pancreatic neuroendocrine tumor were included. The associations between clinicopathological parameters and prognosis were evaluated statistically. Efficiencies of different thresholds for tumor size, mitotic count, and Ki67 proliferation index for prognosis prediction were compared. Vascular invasion was statistically associated with high tumor grade, advanced pT stage, and mortality rate. The presence of non-functional tumor, lymphatic invasion, and > 10 cm tumor size were significantly related to shorter overall survival. Advanced pT stage (pT3-4), > 5 cm tumor size, and high tumor grade (grades 2-3) were significantly associated with shorter disease-free survival. The mortality rate showed the strongest statistical significance with mitotic count when grouped as 1: < 2, 2: 2-10, and 3: > 10 mitosis/ 2 mm². The 10% threshold value for Ki67 index was more successful in predicting adverse prognosis. Among the morphologic variants, the ductulo-insular variant was the most promising to have positive prognostic value in our series, although no statistical significance was detected. In conclusion, threshold values of 5 cm and 10 cm for tumor size, 10% for Ki67 proliferation index, and 10/2 mm² for mitotic count and vascular and lymphatic invasion assessed separately are potential prognostic candidates for better stratification of panNETs.

A Case of Adult Pancreatoblastoma With Novel APC Mutation and Genetic Heterogeneity

Background

Pancreatoblastoma is a rare malignant epithelial neoplasm of the pancreas that mainly occurs in children and involves abnormalities in the WNT/β-catenin pathway, such as CTNNB1 mutation. However, the molecular abnormalities in adult pancreatoblastoma are not well known.

Case Presentation

An elderly man, who underwent elective distal pancreatectomy and splenectomy, was referred to our hospital with a mass in the tail of the pancreas. Histologically, the lesion revealed proliferation of clear, basophilic, and cartilaginous tumor cells with lymphatic metastasis. Each of the morphologically distinct tumor components showed different immunohistochemical patterns, indicating heterogeneous differentiation, including epithelial (both acinar and ductal), mesenchymal, and neuroendocrine differentiation. All tumor components showed nuclear expression of β-catenin and cyclin D1. Per next-generation sequencing (NGS), the clear and basophilic tumor cells shared mutations in APC, GRM8, LAMP1, and AKA9. Among the mutations, APC, c.1816_1817insA showed the highest frequency in both cell types, indicating that APC mutation was a driver mutation of the tumor. A diagnosis of PB was rendered.

Summary

In conclusion, the clear and basophilic cells of the tumor were supposedly derived from the same clone and subsequently acquired additional mutations. This is the first report of clonal evolution in pancreatoblastoma.

Pancreatic Solid Pseudopapillary Neoplasm: Key Pathologic and Genetic Features

CONTEXT.—

Solid pseudopapillary neoplasm of the pancreas is a low-grade malignant tumor generally associated with a good prognosis. Solid pseudopapillary neoplasms show peculiar morphologic features, but sometimes the differential diagnosis with other pancreatic neoplasms (ie, pancreatic neuroendocrine tumors) can be a challenging task, especially in cytologic or biopsy specimens. In these cases immunohistochemistry is a useful tool, but the diagnostic utility of several proposed immunohistochemical markers is questionable. In recent years, despite several attempts to characterize the pathogenetic, molecular, and prognostic features of solid pseudopapillary neoplasms, they still remain unclear.

OBJECTIVE.—

To give the reader a comprehensive update on this entity.

DATA SOURCES.—

The PubMed database (US National Library of Medicine) was searched using the following string: pseudopapillary tumor [AND/OR] neoplasm [AND/OR] pancreas. All articles written in English were included. In addition, because a heterogeneous terminology has been used in the past to define solid pseudopapillary neoplasms, the reference lists of each paper selected in the PubMed database were also reviewed.

CONCLUSIONS.—

This review gives a comprehensive update on the pathologic, clinical, and molecular features of solid pseudopapillary neoplasms, particularly addressing issues and challenges related to diagnosis. In addition, we have tried to correlate the molecular alterations with the morphologic and clinical features.

Pancreatic neuroendocrine neoplasms: Clinicopathological features and pathological staging

The nomenclature and classification of pancreatic neuroendocrine neoplasms has evolved in the last 15 years based on the advances in knowledge of the genomics, clinical behaviour and response to therapies. The current 2019 World Health Organization classification of pancreatic neuroendocrine neoplasms categorises them into three groups; pancreatic neuroendocrine tumours (PanNETs)(grade 1 grade 2, grade 3), pancreatic neuroendocrine carcinomas and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) based on the mitotic rate, Ki-67 index, morphological differentiation and/or co-existing tissue subtype. PanNETs are also classified into non-functional NET, insulinoma, gastrinoma, VIPoma, glucagonoma, somatostatinoma, ACTH-producing NET and serotonin producing NET based on hormone production and clinical manifestations. A portion of the cases were associated with genetic syndromes such as multiple neuroendocrine neoplasia 1 (MEN 1), neurofibromatosis and Von Hippel-Lindau syndrome. In view of the distinctive pathology and clinical behaviour of PanNENs, the current 8th AJCC/UICC staging system has separated prognostic staging grouping for PanNETs from the pancreatic neuroendocrine carcinomas or MiNENs. Pancreatic neuroendocrine carcinomas and MiNENs are staged according to the prognostic stage grouping for exocrine pancreatic carcinoma. The new stage grouping of PanNETs was validated to have survival curves separated between different prognostic groups. This refined histological and staging would lead to appropriate selections of treatment strategies for the patients with pancreatic neuroendocrine neoplasms.

Molecular Pathology of Well-Differentiated Gastro-entero-pancreatic Neuroendocrine Tumors

Well differentiated neuroendocrine tumors (NETs) arising in the gastrointestinal and pancreaticobiliary system are the most common neuroendocrine neoplasms. Studies of the molecular basis of these lesions have identified genetic mutations that predispose to familial endocrine neoplasia syndromes and occur both as germline events and in sporadic tumors. The mutations often involve epigenetic regulators rather than the oncogenes and tumor suppressors that are affected in other malignancies. Somatic copy number alterations and miRNAs have also been implicated in the development and progression of some of these tumors. The molecular profiles differ by location, but many are shared by tumors in other sites, including those outside the gastroenteropancreatic system. The approach to therapy relies on both the neuroendocrine nature of these tumors and the identification of specific alterations that can serve as targets for precision oncologic approaches.

Morphologic Variants of Pancreatic Neuroendocrine Tumors: Clinicopathologic Analysis and Prognostic Stratification

Better prognostication/stratification of pancreatic neuroendocrine tumors (PanNETs) is needed. In this detailed morpheomic study of 163 resected PanNETs, 11 unusual variants, some of which were not previously recognized, and others scarcely documented in the literature, were identified, and their pathologic characteristics were further analyzed. By behavior and clinicopathologic associations, these variants could be grouped into three prognostically different categories. I. More aggressive (20%). Included in this group were the variants that in average showed higher grade and stage and adverse outcome including oncocytic, plasmacytoid, lipid-rich and previously unrecognized hepatoid variants, which often had a more diffuse/broad-band growth pattern, with some also displaying discohesiveness. They were characterized by abundant cytoplasm and often had prominent nucleoli (as seen in metabolically active cells), thus the provisional name "metabolic cell phenotype." Because of their diversion from classical neuroendocrine cytomorphology, these variants created challenges on original diagnostic workup, particularly hepatoid examples, which revealed Arginase 1/Hep Par-1 expression in 50%. II. Less aggressive (10%). These cases either showed signs of maturation, including nested growth, paraganglioid pattern (which was previously unrecognized), and organoid PanNETs such as "ductulo-insular" growth, or showed symplastic/degenerative changes, and despite their paradoxically disconcerting histology, were more benevolent in behavior. III. Undetermined. There were other variants including mammary tubulolobular-like, pseudoglandular, peliotic, and sclerotic PanNETs, which although diagnostically challenging, their biologic significance could not be determined because of rarity or heterogeneous characteristics. Prognostic associations: Features that were significantly different in the more aggressive group than the less aggressive group were median size (5.0 vs 1.6 cm, p < 0.001), percentage of pT3+T4 cases (72% vs 12%, p < 0.001), Ki67 index (5.3% vs 2.3%, p = 0.001), % G2 and G3 cases (77% vs 27%, p < 0.001), and rate of lymph node and distant metastasis (96% vs 27%, p < 0.001). In stepwise logistic regression model using the 3 established prognosticators of T stage, size, and grade along with morphology, only aggressive-morphology (metabolic cell phenotype) was found to be associated with metastatic behavior with an odds ratio of 5.9 with 95% confidence interval (C.I.) 1.688 to 22.945 and p value 0.007. In conclusion, PanNETs display various morphologic patterns that are not only challenging and important diagnostically but appear to have biologic significance. Tumors with more diffuse growth of cells with nucleoli and abundant cytoplasm and/or discohesion (oncocytic, hepatoid, lipid-rich, plasmacytoid PanNETs), provisionally termed "metabolic cell phenotype," show aggressive characteristics and are an independent determinant of adverse outcome and thus may require closer post-surgical follow-up, whereas variants with more degenerative or mature features (ductuloinsular, pleomorphic, paraganglioma-like) appear to be more benevolent despite their more atypical and worrisome morphology.

Primary signet ring cell carcinoma of the pancreas: Cytopathology review of a rare entity

Primary signet ring cell carcinoma of the pancreas (PSRCCP) is an extremely rare diagnosis that has not been extensively studied in literature. Primary and metastatic neoplasms to the pancreas may exhibit cytomorphological similarities to signet ring cells, posing diagnostic challenges. In this article, we review PSRCCP and provide a study of several primary pancreatic neoplasms that may mimic the appearance of PSRCCP upon cytopathology evaluation, shedding light on the existence of this dilemma, and helping cytopathologists in navigating similar scenarios in their practice.

A Clinicopathologic and Molecular Update of Pancreatic Neuroendocrine Neoplasms With a Focus on the New World Health Organization Classification

CONTEXT.—

According to the 2017 World Health Organization classification, pancreatic neuroendocrine neoplasms (PanNENs) include a new category of pancreatic neuroendocrine tumor, grade 3, which is often difficult to differentiate from pancreatic neuroendocrine carcinoma. However, pancreatic neuroendocrine tumor grade 3 and pancreatic neuroendocrine carcinoma are distinct entities with very different clinical presentation, prognosis, and therapeutic strategies. Recent discoveries on the molecular characteristics of pancreatic neuroendocrine tumors also play an essential role in the pathologic differential diagnosis of PanNENs. In addition, the histopathologic varieties of PanNENs bring in many differential diagnoses with other pancreatic neoplasms, especially acinar cell carcinoma, solid pseudopapillary neoplasm, and ductal adenocarcinoma.

OBJECTIVE.—

To provide a brief update of the World Health Organization classification; the clinical, histopathologic, immunohistochemical, and molecular characteristics; and the differential diagnoses and biological behavior of PanNENs.

DATA SOURCES.—

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

CONCLUSIONS.—

The evolving clinical, histopathologic, immunohistochemical, and molecular features of PanNENs are reviewed. Important differential diagnoses with other neoplasms of the pancreas are discussed.

Synchronous pancreatic tumors in a patient with history of Wilms tumor: A case of pancreatic adenocarcinoma and lipid-rich neuroendocrine tumor diagnosed by cytopathology

Synchronous tumors represent a very small portion of pancreatic tumors. Although there is a higher incidence of secondary malignant neoplasms (SMN) in patients with history of Wilms tumor (WT), pancreatic tumors are very infrequent SMNs in this population. We report the first case of synchronous pancreatic tumors in a patient with history of WT. Two separated pancreatic lesions were identified by abdominal computerized tomography (CT) scan. Fine-needle aspiration of both lesions was performed for cytopathology examination. A pancreatic adenocarcinoma was diagnosed in the head of pancreas, and the pancreatic body lesion was found to be a neuroendocrine tumor (NET). The NET had characteristic vacuolated lipid-rich cytoplasm. Further molecular testing was done on both tumors, but no common cancer-associated mutation was found.

Immunohistochemical Biomarkers of Gastrointestinal, Pancreatic, Pulmonary, and Thymic Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) are a heterogeneous group of epithelial neoplastic proliferations that irrespective of their primary site share features of neural and endocrine differentiation including the presence of secretory granules, synaptic-like vesicles, and the ability to produce amine and/or peptide hormones. NENs encompass a wide spectrum of neoplasms ranging from well-differentiated indolent tumors to highly aggressive poorly differentiated neuroendocrine carcinomas. Most cases arise in the digestive system and in thoracic organs, i.e., the lung and thymus. A correct diagnostic approach is crucial for the management of patients with both digestive and thoracic NENs, because their high clinical and biological heterogeneity is related to their prognosis and response to therapy. In this context, immunohistochemistry represents an indispensable diagnostic tool that pathologists need to use for the correct diagnosis and classification of such neoplasms. In addition, immunohistochemistry is also useful in identifying prognostic and theranostic markers. In the present article, the authors will review the role of immunohistochemistry in the routine workup of digestive and thoracic NENs.

Primary pancreatic perivascular epithelioid cell tumor (PEComa): A surgical enigma. A systematic review of the literature

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor, with distinctive morphology and expression of myo-melanocytic markers. Current scientific literature reported just 24 cases of pancreatic PEComas. With our systematic review, we aimed at improving our understanding of the disease, focusing on the knowledge gained on epidemiology, etiology, clinical presentation, diagnosis, treatment and prognosis.

METHODS

Based on the PRISMA guidelines, a systematic research was carried out on PubMed/MEDLINE, Web of Science, Scopus, EMBASE, and EBSCO using the search terms: ("perivascular epithelioid cell tumor" OR ″PEComa") and ("pancreas "OR″ pancreatic").

RESULTS

The 4th-6th decades of life and female sex (86.9%) turned out as the most affected. Pancreatic head was the most involved site (50%), with a single lesion in almost all cases. The diagnosis was only obtained after histopathological examination (70.8%). The clinical presentation was non-specific, abdominal pain being the main symptom (60.9%). At immunohistochemistry, PEComa showed benign epithelioid predominance and a strong positivity for HMB-45, Melan-A, and α-SMA. Surgical resection was performed in almost all cases, while for one patient the multidisciplinary group chose just endoscopic and imaging follow-up, based on the benign nature of the lesion.

CONCLUSIONS

The biological characteristics of pancreatic PEComa remain an enigma. Its prognosis seems to depend on whether atypical ("worrisome") histological features are available or not. Surgery turned out as the most appropriate treatment, without reaching any agreement on surgery timing. Further studies on larger population are needed to better understand the biological features of pancreatic PEComa, in order to set up guidelines in the diagnosis, treatment and follow-up.

Two unusual variants of pancreatic neuroendocrine tumor and their potential pitfalls on fine-needle aspiration cytology

Endoscopic ultrasound-guided fine-needle aspiration is increasingly utilized for the diagnosis of pancreatic lesions. Although operator dependent, the procedure has good overall performance characteristics and is minimally invasive; however, accuracy and sensitivity are reportedly lower for pancreatic neuroendocrine tumor (PanNET) compared with the more common pancreatic ductal adenocarcinoma (pACA). The underperformance is further exacerbated by the unusual cases of PanNET presenting with variant cytomorphology. We report two separate diagnostically challenging cases: a pigmented PanNET and a clear cell PanNET. We briefly review the literature and emphasize the importance of recognizing these uncommon variants when encountered in aspirate material. Diagn. Cytopathol. 2017;45:371-378. © 2016 Wiley Periodicals, Inc.

Clear cell neuroendocrine tumor of pancreas: Endoscopic Ultrasound-guided fine needle aspiration diagnosis of an uncommon variant

The cytomorphologic features of clear cell neuroendocrine tumor of pancreas have been rarely reported in cytology literature. The cytomorphology of this rare variant mimics many primary and metastatic clear cell tumors of the pancreas. However, a precise cytological diagnosis can be rendered by awareness of this entity and judicious use of immunohistochemistry. We report one such case in a young woman diagnosed on endoscopic ultrasound fine needle aspiration. The tumor cells showed positive staining with synaptophysin, chromogranin, and also with inhibin.

Acinar Cell Carcinoma of the Pancreas: Overview of Clinicopathologic Features and Insights into the Molecular Pathology

Acinar cell carcinomas (ACCs) of the pancreas are rare pancreatic neoplasms accounting for about 1–2% of pancreatic tumors in adults and about 15% in pediatric subjects. They show different clinical symptoms at presentation, different morphological features, different outcomes, and different molecular alterations. This heterogeneous clinicopathological spectrum may give rise to difficulties in the clinical and pathological diagnosis with consequential therapeutic and prognostic implications. The molecular mechanisms involved in the onset and progression of ACCs are still not completely understood, although in recent years, several attempts have been made to clarify the molecular mechanisms involved in ACC biology. In this paper, we will review the main clinicopathological and molecular features of pancreatic ACCs of both adult and pediatric subjects to give the reader a comprehensive overview of this rare tumor type.

Clear cell carcinoid of the appendix: Report of two cases with literature review

The clear cell/lipid-rich change has been described in neuroendocine tumors in several organs, but rarely observed in the appendix. In this study, we describe the morphologic, immunohistochemical features of incidentally discovered appendiceal carcinoids entirely represented by clear cells in a 22-year-old man and a 52-year-old woman. Ultrastructual examination demonstrated abundant lipid droplets and dense core granules. The mechanism leading to lipid accumulation in the cytoplasm has not been discovered, but degenerative processes following recurrent inflammatory change might be considered. This uncommon variant of appendiceal classic carcinoid tumors may bear a superficial resemblance to goblet carcinoid and/or appendiceal metastases from clear cell carcinoma. Awareness of clear cell carcinoid of the appendix will prevent incorrect diagnosis and unnecessary aggressive management.

Pathology diagnosis of pancreatic neuroendocrine tumors

Histopathology of pancreatic neuroendocrine tumors (PNETs) typically displays characteristic features. However, pathologists may encounter histological variants that may resemble other pancreatic tumors. Immunohistochemistry is a powerful tool in confirming neuroendocrine differentiation and differentiating PNETs with other pancreatic neoplasms. Histopathological features could be associated with inherited syndromes. Once the pathology diagnosis of neuroendocrine tumor was made, an accurate grading based on World Health Organization (WHO) classification is required. This review will focus on histology variants, immunohistochemistry and WHO classification of PNET.

Pancreatic Neuroendocrine Neoplasms

Pancreatic neuroendocrine neoplasms (Pan-NENs) are rare but clinically important lesions. Pan-NENs are known for and often categorized by their capacity to produce clinical syndromes mediated by the production of hormones. Despite sometimes presenting dramatically from excessive hormone production, not all Pan-NENs produce functional hormone, and they can pose diagnostic challenges to practicing pathologists. Distinguishing Pan-NENs from mimics can be crucial, because Pan-NENs carry different prognoses and have unique treatments available due to their specific biological properties. This article reviews the current categorization and features of Pan-NENs.

Cytologic features of lipid-rich variant of pancreatic endocrine tumor-report of two cases with literature review

Pancreatic endocrine tumor (PET) is an uncommon neoplasm of the pancreas with distinct cytomorphologic features. Lipid-rich PET, a rare variant, histologically deviates from that of a conventional PET. There is only one case report of the cytologic features of this rare entity in the literature. We report two cases of lipid-rich PETs diagnosed by endoscopic ultrasound-guided FNA biopsy. Case 1 showed large aggregates, small clusters, and single cells with plasmacytoid appearance, small uniform nuclei, coarse chromatin, and prominent nucleoli. Abundant distinct small cytoplasmic vacuoles were present in almost all tumor cells and the background was clean. Case 2 showed flat cohesive sheets of medium-sized uniform cells with indistinct plasmacytoid appearance, uniform nuclei, fine and evenly distributed chromatin, and inconspicuous nucleoli. Distinct small cytoplasmic vacuoles were seen only focally. Immunohistochemical stains in cell blocks of both cases confirmed the diagnosis of PET. Lipid-rich PET may be misinterpreted on cytology specimens if the pathologist is not aware of this rare entity since it mimics clear cell carcinoma of the kidney, adrenal cortical neoplasm, or adenocarcinoma of the pancreas.

Intraductal polypoid lipid-rich neuroendocrine tumor of the pancreas with entrapped ductules: case report and review of the literature

Pancreatic neuroendocrine tumors of the main pancreatic duct are rare and usually small due to symptoms of pancreatic duct obstruction. We present a case of a large (3 cm), well-differentiated (G1) lipid-rich polypoid neuroendocrine tumor of the pancreas completely occluding the main pancreatic duct with non-neoplastic-entrapped ductules and CK19 positivity. Clinical, radiological, gross, microscopic, immunohistochemical, and ultrastructural findings are discussed. The literature pertaining to the unique features of this case is reviewed including clinical and pathologic pitfalls and the possible etiologic and prognostic significance of these findings.

Lipid-rich ("clear cell") neuroendocrine tumors of the pancreas in MEN I patients

The presence of "clear" or lipid-rich cells within pancreatic neuroendocrine tumors is thought to be pathognomonic of von Hippel-Lindau (VHL) disease, especially in the context of multiple tumors. However, we encountered the presence of lipid-rich cells in six of 16 patients (eight microadenomas/adenomas) who had multiple endocrine neoplasia type I (MEN I). Three of the lesions (two microadenomas and one adenoma) were composed entirely of lipid-rich cells while the remaining five lesions had a component of lipid-rich cells. All lesions containing lipid-rich cells were negative for α-inhibin, but positive for chromogranin and synaptophysin. In addition, four of the eight lesions were glucagon positive. None of the patients had clinical symptoms related to hormone production. We suggest that lipid-rich cells are not reflexly indicative of VHL, and that they may be encountered in a proportion of cases of MEN I either focally or constituting the entire neuroendocrine lesion.

Pancreatic PEComa: a case report with ultrastructural localization of HMB-45 within melanosomes

PEComas (perivascular epithelioid cell tumors) represent a group of mesenchymal neoplasms showing characteristic morphologic, immunohistochemical, ultrastructural, and genetic features. These neoplasms are usually considered benign, being often well circumscribed by a thin capsule and showing scarce atypia. However, in some cases, they show local invasion and multiple metastases and cause the patient's death. PEComas have been found in many locations, but only 7 cases have been described in the pancreas to date. Here, the authors report an additional case of this rare neoplasm and demonstrate the HMB-45 immunoreactivity of melanosomes or premelanosomes at the ultrastructural level.

Endocrine tumours of the pancreas

Verbeke C S (2010) Histopathology 56, 669-682 Endocrine tumours of the pancreas Histopathology reporting of pancreatic endocrine neoplasms is complex. The tumours can exhibit a variety of morphological appearances, which often require careful differential diagnostic consideration. Prediction of tumour behaviour and clinical outcome is based on the World Health Organization classification and TNM staging and grading system, which share some criteria and premises, but differ significantly in others. Clinicopathological correlation through discussion at multidisciplinary team meetings is of paramount importance. In this review special emphasis is given to the items of information that can and should be provided by the pathologist to allow optimal patient management. The review further discusses areas of current controversy and uncertainty, of which pathologists participating in multidisciplinary discussions should be aware.

Lipid-rich variant of appendiceal well-differentiated endocrine tumor (carcinoid)

Well-differentiated endocrine tumors (WDETs) of the appendix show characteristic morphologic features, including proliferation of cells with finely granulated eosinophilic cytoplasm. However, clear cell WDETs, which can present a diagnostic challenge, have been occasionally described, but it is unknown whether they represent a morphologic variant with distinct clinicopathologic features. Moreover, the clear cell appearance of the cytoplasm has never been explained. We studied 13 appendiceal WDETs composed of clear cells, which showed an immunophenotype identical to that of conventional appendiceal WDETs. Ultrastructural examination demonstrated abundant lipid accumulation. Patient survival was excellent and equal to that of conventional appendiceal WDETs. These neoplasms, which represent a lipid-rich variant of appendiceal WDETs, do not have different relevant clinical implications compared with conventional WDETs, but it is important to know of their existence for the differential diagnosis with more aggressive neoplasms, including goblet cell carcinoids and appendiceal metastases from clear cell carcinomas.

Lipid-rich and clear cell neuroendocrine tumors ("carcinoids") of the appendix: potential confusion with goblet cell carcinoid

The so-called clear cell change has been described in neuroendocrine tumors at several locations. Those associated with von Hippel Lindau disease are pathognomonically "clear" and the cytoplasmic appearance has been ascribed to intracytoplasmic lipid. However, lipid has not been demonstrated in all cases of clear cell carcinoid tumors. Such variants have not been described in carcinoid tumors of the appendix and cases with a prominent proportion of clear or more correctly, lipid-rich cytoplasm may bear a superficial resemblance to goblet cell carcinoid and/or signet ring adenocarcinoma. Seven cases, in 5 females and 2 males ranging in age from 22 to 65 years, were noted to have a population of lipid-rich and vacuolated clear cells accounting for 25% or more of the tumor population. The carcinoid tumors were incidental in all cases with 4 of patients presenting with appendicitis, 2 with concomitant mucinous cystadenocarcinomas of the appendix and 1 with an adenocarcinoma of the ascending colon. Morphologically, the tumors had a nested and trabecular pattern and were composed of an admixture of microvesicular and clear lipid-rich cells. There were no mitoses, areas of necrosis of lymphovascular invasion and all cases extended to the mesoappendix. All cases were positive for synaptophysin, chromogranin, and serotonin but negative for inhibin. Three cases were examined ultrastructurally, and showed the presence of intracytoplasmic lipid and neurosecretory granules. None of the patients have shown evidence of recurrent disease. The importance of recognizing this variant of carcinoid tumor in the appendix is to avoid confusion with goblet cell carcinoid tumors with or without a signet ring adenocarcinoma. The presence of multi-vacuolated, foamy and clear cells, some resembling signet ring or goblet cells, in otherwise classic carcinoid tumors is rare but should be considered in this context in the appendix.

A tissue microarray-based comparative analysis of novel and traditional immunohistochemical markers in the distinction between adrenal cortical lesions and pheochromocytoma

We have encountered an increasing number of image-guided adrenal mass biopsies in which the differential diagnosis is adrenal cortical lesion versus pheochromocytoma. This distinction is sometimes difficult because of confounding clinical presentations, overlapping morphologies, and some degree of immunophenotypic overlap including focal staining with markers of purported lineage specificity. Interventional radiologists commonly use narrow gauge biopsy needles in this setting, which yield scant diagnostic tissue and further complicate pathologic evaluation. In this study, a detailed immunoprofile of 63 adrenal cortical lesions (3 adrenal rests, 6 adrenal cortical hyperplasias, 43 adrenal cortical adenomas, 4 adrenal cortical neoplasms of uncertain malignant potential, and 7 adrenal cortical carcinomas) was compared with 35 pheochromocytomas using traditional (calretinin, chromogranin, inhibin, melanA, and synaptophysin) and novel [steroidogenic factor-1 (SF-1), microtubule-associated protein 2, and mammalian achaete-scute homolog-1] antibodies, using tissue microarray technology to simulate small image-guided biopsies. Staining extent and intensity were each scored semiquantitatively for each antibody. A comparison of sensitivity and specificity using different intensity thresholds required for a "positive" result (> or = 1+ vs. > or = 2+) was performed. Staining results based on a > or = 1+ and (> or = 2+) intensity threshold were as follows: calretinin-95% (89%) in adrenal cortical lesions and 14% (0%) in pheochromocytomas; chromogranin-0% in adrenal cortical lesions and 100% in pheochromocytomas; inhibin-97% (86%) in adrenal cortical lesions and 6% (0%) in pheochromocytomas; microtubule-associated protein 2-29% (16%) in adrenal cortical lesions and 100% (89%) in pheochromocytomas; mammalian achaete-scute homolog-1-0% in both adrenal cortical lesions and pheochromocytomas; melanA-94% (86%) in adrenal cortical lesions and 6% (0%) in pheochromocytomas; SF-1-87% (86%) in adrenal cortical lesions and 0% in pheochromocytomas; synaptophysin-67% (59%) in adrenal cortical lesions and 100% in pheochromocytomas. Using an antibody panel consisting of chromogranin plus the nuclear antibody SF-1 and either calretinin or inhibin, while requiring a high-staining intensity threshold, helps to eliminate interpretative issues of artifactual or background reactivity, improves diagnostic sensitivity/specificity, and makes for an effective immunohistochemical approach in distinguishing adrenal cortical lesions from pheochromocytomas.

Endoscopic ultrasound-guided fine-needle aspiration diagnosis of clear-cell pancreatic endocrine neoplasm in a patient with von Hippel-Lindau disease: a case report

The cytologic findings of a clear-cell pancreatic endocrine neoplasm (PEN) diagnosed by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) occurring in a 29-year-old man with von Hippel-Lindau (VHL) syndrome are described. Imaging studies showed multiple pancreatic masses and cysts, a single liver lesion, and pulmonary and renal cysts. Cytologic features of this clear-cell PEN included the presence of large sheets and rounded clusters of polygonal neoplastic cells with relatively abundant cytoplasm containing numerous, small, sharply-demarcated vacuoles that occasionally indented nuclei and gave the cells a "frothy" appearance. Mild anisonucleosis was present and nucleoli were visible. Rare single cells and stripped nuclei were seen. Small vessels transgressed tumor cell sheets. These cytologic findings are distinct from those of typical endocrine neoplasms, and bear resemblance to the cytologic features of renal cell carcinoma metastatic to the pancreas. To the best of our knowledge, this is the first detailed report of the EUS-FNA cytologic findings of a clear-cell PEN associated with VHL syndrome. We believe that the distinctive and characteristic cytologic features, together with immunohistochemical studies, can allow a preoperative cytologic diagnosis of this highly unusual pancreatic lesion and avoid possible confusion with other clear-cell neoplasms in the pancreas, particularly metastatic renal cell carcinoma.

Endocrine neoplasms of the pancreas: pathologic and genetic features

CONTEXT

Pancreatic endocrine neoplasms (PENs) are diagnostically challenging tumors whose natural history is largely unknown. Histopathology allows the distinction of 2 categories: poorly differentiated high-grade carcinomas and well-differentiated neoplasms. The latter include more than 90% of PENs whose clinical behavior varies from indolent to malignant and cannot be predicted by their morphology.

OBJECTIVES

To review the literature and report on additional primary material about the clinicopathologic features, classification, staging, grading, and genetic features of PENs.

DATA SOURCES

Literature review of relevant articles indexed in PubMed (US National Library of Medicine) and primary material from the authors' institution.

CONCLUSIONS

The diagnosis of PEN is generally easy, but unusual features may induce misdiagnosis. Immunohistochemistry solves the issue, provided that the possibility of a PEN has been considered. Morphology allows the distinction of poorly differentiated aggressive carcinomas from well-differentiated neoplasms. The World Health Organization classification criteria allow for the discernment of the latter into neoplasms and carcinomas with either benign or uncertain behavior. The recently proposed staging and grading systems hold great promise for permitting a stratification of carcinomas into clinically significant risk categories. To date, inactivation of the MEN1 gene remains the only ascertained genetic event involved in PEN genesis. It is inactivated in roughly one-third of PENs. The degree of genomic instability correlates with the aggressiveness of the neoplasm. Gene silencing by promoter methylation has been advocated, but a formal demonstration of the involvement of specific genes is still lacking. Expression profiling studies are furnishing valuable lists of mRNAs and noncoding RNAs that may advance further the research to discover novel markers and/or therapeutic targets.

Clear cell carcinoma of the pancreas: histopathologic features and a unique biomarker: hepatocyte nuclear factor-1beta

Clear cell carcinoma as a variant of ductal carcinoma of the pancreas is not well recognized. Hepatocyte nuclear factor-1beta as a transcription factor has been identified as a specific biomarker of clear cell tumor of the female genital tract. The aim of this study was to systematically analyze clear cell carcinoma of the pancreas and its unique biomarker hepatocyte nuclear factor-1beta. A total of 84 pancreatic adenocarcinomas were analyzed pathologically and with an immunohistochemical approach with hepatocyte nuclear factor-1beta antibody. The identified clear cell carcinomas were further studied by PAS, DPAS, and mucicarmine stains. Pathologic features and clinical follow-up were documented. Of them, 20 (24%) pancreatic adenocarcinomas were identified with clear cell features, including 12 clear cell carcinomas and 8 ductal adenocarcinomas with clear cell component (defined as less than 75% of tumor with clear cells). Cytologically, the clear cell carcinomas exhibited clear cytoplasm with centrally located, atypical nuclei. PAS, DPAS, and mucicarmine stains confirmed that the clear cytoplasm was not due to accumulation of glycogen or mucin. The results of immunostaining showed that hepatocyte nuclear factor-1beta is overexpressed in all clear cell carcinomas and in the clear cell components of eight ductal carcinomas with clear cell features. In contrast, in usual ductal adenocarcinoma, hepatocyte nuclear factor-1beta exhibited overall weak or focally moderate staining; only eight cases were strongly positive (15%) of which 38% were high grade and 63% were moderate grade. However, when included with the strong staining cases in mixed and clear cell carcinoma, this group regardless of morphology appeared to correlate with worse survival compared to the group with weak hepatocyte nuclear factor-1beta staining across morphologies (P<0.01). Thus, clear cell carcinoma of the pancreas is not an uncommon variant of pancreatic ductal adenocarcinoma. Hepatocyte nuclear factor-1beta is a useful marker to identify these clear cell carcinomas, and its overexpression may aid in stratifying survival rate.