Neuroendocrine neoplasms of the biliary tree, liver and pancreas: a pathological approach

Practical hints for the diagnosis of mixed neuroendocrine-non-neuroendocrine neoplasms of the digestive system

In this editorial, a comment on the article by Díaz-López et al published in the recent issue of the 2024 is provided. We focus on the practical implications critical for providing a correct and complete diagnosis of mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) in the gastrointestinal system. The diagnosis of MiNEN begins with the recognition of neuroendocrine features in one component of a biphasic tumor. The non-neuroendocrine counterpart can be virtually represented by any neoplastic type, even though the most frequent histologies are glandular and squamous. However, qualification of the neuroendocrine component requires histological and immunohistochemical confirmation. Neuroendocrine tumors are characterized by a peculiar architectural organization and bland nuclei with granular “salt and pepper” chromatin. Although neuroendocrine carcinomas have multiple and variable presentations, they typically show a solid or organoid architecture. The histological aspect needs to be confirmed by immunohistochemistry, and a diagnosis is confirmed whenever the expression of keratin and neuroendocrine markers is observed. Once both histopathological and immunohistochemical features of neuroendocrine neoplasms are identified, it is important to consider the three major pitfalls of MiNEN diagnostics: (1) Entrapment of neuroendocrine non-neoplastic cells within the tumor mass; (2) Differential diagnosis with amphicrine neoplasms; and (3) Differential diagnosis of tumors that partially express neuroendocrine markers. According to the current guidelines for diagnosing digestive MiNEN, each component must represent at least 30% of the entire neoplastic mass. Although the high-grade histopathological subtype frequently determines disease prognosis, both components can significantly affect prognosis. Thus, if one of the components, either neuroendocrine or non-neuroendocrine, does not fulfill the volumetric criteria, the guidelines still encourage reporting it. These strict criteria are essential for correctly recognizing and characterizing digestive MiNENs. This task is essential because it has prognostic relevance and substantial potential value for guiding further studies in this field. In the future, systematic analyses should be performed to validate or reconsider the current 30% cutoff value.

Rare and lacking typical clinical symptoms of liver tumors: Four case reports

BACKGROUND

Rare liver tumors (RLTs) have an extremely low likelihood of forming, and some have been recorded only in isolated cases. The lack of normal clinical symptoms in RLTs makes preoperative diagnosis extremely challenging, which results in frequent misinterpretation. The present case report helps enhance our ability to recognize and treat uncommon liver tumor disorders.

CASE SUMMARY

We describe four distinct examples of rare liver tumor diseases. These cases were all true cases with no conventional clinical signs or imaging findings. In all patients, hepatic occupancy was discovered on physical examination, which raised the preoperative suspicion of hepatic cancer. All tumors were surgically removed, and postoperative histology and immunohistochemistry were performed to confirm the diagnosis. The first patient had primary hepatic fibrosarcoma. The second case involved a primary hepatic neuroendocrine tumors. These two patients had malignant liver tumors, and both had extremely satisfactory surgical outcomes. The third case involved focal hepatic steatosis, and the fourth case involved a single necrotic nodule in the liver. These two patients had benign liver tumors, but they had already undergone surgery and did not require any postoperative care.

CONCLUSION

The number of patients with RLTs is small, and the clinical and imaging results are vague. Preoperative diagnosis is challenging, and patients are sometimes mistakenly diagnosed with liver cancer, which leads to unnecessary surgical therapy in certain individuals.

Co-existing Neuroendocrine Tumors in the Ileum and Pancreas: A Clinico-Pathological Challenge

Ileal (I) and pancreatic (Pan) neuroendocrine tumors (NETs) are among the most common digestive neuroendocrine neoplasms (NENs). Coexisting NETs at both sites are rare, and establishing the primary or metastatic nature of the two lesions may be crucial for the appropriate treatment. We reviewed all the clinical reports of patients with INETs or PanNETs, diagnosed and treated in our ENETS Center of Excellence between 2012 and 2022. We selected patients with a history of synchronous or metachronous neuroendocrine (NE) lesions at the ileum and pancreas. For those with available histological samples from both sites, an immunohistochemistry (IHC) analysis for CDX2, Islet1, and serotonin has been performed. We found seven patients with NET in both the ileum and pancreas. F to M ratio was 4:3, and the median age at first diagnosis was 54 years (42-79). Five cases had synchronous lesions; in 2 cases, PanNETs were diagnosed respectively 8 and 56 months, after INETs. In four patients, with available histological samples from both the sites, a pathologic review and the IHC analysis have been performed, identifying three different scenarios: (i) primary INET metastatic to the pancreas, (ii) primary PanNET metastatic to the ileum, and (iii) synchronous primary PanNET and INET. In our experience, coexisting ileal and pancreatic NENs are rare occurrences. A multidisciplinary evaluation case-by-case and, whenever feasible, a comprehensive histopathological examination are needed to distinguish between metastatic and primary disease, in order to properly treat the patient.

Neoplastic Progression in Neuroendocrine Neoplasms of the Pancreas

CONTEXT.—

Pancreatic neuroendocrine neoplasms (PanNENs) represent a heterogeneous group of epithelial tumors of the pancreas showing neuroendocrine differentiation. These neoplasms are classified into well-differentiated pancreatic neuroendocrine tumors (PanNETs), which include G1, G2, and G3 tumors, and poorly differentiated pancreatic neuroendocrine carcinomas (PanNECs), which are G3 by definition. This classification mirrors clinical, histologic, and behavioral differences and is also supported by robust molecular evidence.

OBJECTIVE.—

To summarize and discuss the state of the art regarding neoplastic progression of PanNENs. A better comprehension of the mechanisms underpinning neoplastic evolution and progression of these neoplasms may open new horizons for expanding biologic knowledge and ultimately for addressing new therapeutic strategies for patients with PanNENs.

DATA SOURCES.—

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

CONCLUSIONS.—

PanNETs can be seen as a unique category, where G1-G2 tumors may progress to G3 tumors mainly driven by DAXX/ATRX mutations and alternative lengthening of telomeres. Conversely, PanNECs display totally different histomolecular features more closely related to pancreatic ductal adenocarcinoma, including TP53 and Rb alterations. They seem to derive from a nonneuroendocrine cell of origin. Even the study of PanNEN precursor lesions corroborates the rationale of considering PanNETs and PanNECs as separate and distinct entities. Improving the knowledge regarding this dichotomous distinction, which guides tumor evolution and progression, will represent a critical basis for PanNEN precision oncology.

Mixed hepatocellular carcinoma and high-grade neuroendocrine neoplasm with ambiguous histopathological features: a case report

Well-differentiated neuroendocrine tumor (NET) and poorly differentiated neuroendocrine carcinoma (NEC) are distinct entities with different biological behavior. However, difficult cases showing equivocal morphology have been reported in some organs. Herein, we report a case of primary hepatic neuroendocrine neoplasm (NEN) with ambiguous histopathological features admixed with conventional hepatocellular carcinoma (HCC). A 70-year-old man with untreated chronic hepatitis B underwent left medial sectionectomy because of two incidental liver masses. On pathological examination, one of the resected tumors had intermingling NEN and HCC components. The NEN component consisted of relatively uniform tumor cells proliferating in trabecular, cord-like, or solid patterns with peripheral nuclear palisading. The tumor cells were immunopositive for synaptophysin, chromogranin A, cluster of differentiation 56 (CD56), and focally hepatocyte paraffin 1. p53 showed wild-type expression. The Ki-67 labeling index was 27% at the hot spot. Eleven months after the surgery, he died of a cerebral hemorrhage without evidence of recurrent liver cancer. The intermediate degree of differentiation and the modest proliferative activity can challenge the distinction between NEC and NET G3. While the coexisting HCC indicates NEC rather than NET in a pathogenetic viewpoint, such ambiguous tumor may not be as aggressive as typical NECs.

Metastatic Neuroendocrine Neoplasms to the Pancreas: Two Unusual Cases and a Review of the Literature

Neuroendocrine tumor metastases to the pancreas are rare, and they share substantial overlap with the significantly more common primary pancreatic neuroendocrine neoplasms, representing a potential diagnostic pitfall. Elucidating whether a neuroendocrine tumor within the pancreas is a primary neoplasm versus a metastasis has significant prognostic and treatment implications. Correlation with clinical history and imaging as well as incorporating an appropriate immunohistochemical panel are essential to establish the correct diagnosis. Herein, we present 2 rare neuroendocrine tumors that metastasized to the pancreas: a medullary thyroid carcinoma and an atypical carcinoid tumor of lung origin. We also provide a brief review of the literature.

Primary hepatic functional neuroendocrine tumor in an elderly female: Case report

Key Clinical Message

Primary hepatic neuroendocrine tumor, an exceptionally rare subtype, poses a diagnostic challenge. Oncological resections should be considered, even in elderly patients after following protocolized pre-operative optimizations.

Abstract

Neuroendocrine tumors (NETs) are rare tumors that primarily develop in the gastrointestinal and respiratory tracts. While the liver is commonly affected by NET metastases, primary hepatic neuroendocrine tumors (PHNETs) are an exceptionally rare subtype. The characteristic slow growth and nonfunctional nature of PHNETs pose challenges in their diagnosis. Furthermore, PHNETs often exhibit a lack of unique radiological characteristics that differentiate them from other liver tumors, leading to frequent misdiagnosis as hepatocellular carcinoma. We performed left hepatectomy for PHNET in an elderly lady with prolonged stormy postoperative course. This case report of a PHNET highlights the importance of histopathology and immunohistochemistry in the diagnosis and emphasizes that oncological resection, if feasible, is the preferred treatment even in the elderly population.

Comparison of the clinical features and long-term prognosis of gallbladder neuroendocrine carcinoma versus gallbladder adenocarcinoma: A propensity score-matched analysis

Gallbladder neuroendocrine carcinoma (GBNEC) is rare and characterized by a low degree of tumor differentiation. The clinical features of GBNEC versus gallbladder adenocarcinoma (GBADC) remain a subject of debate. A total of 201 GBADC and 36 GBNEC cases that underwent surgery resection between January 2010 and 2022 at the Department of Biliary Surgery, West China Hospital, Sichuan University were included. A 1:1 propensity score matching (PSM) was performed based on seven predefined variables: age, sex, the American Joint Committee on Cancer (AJCC) stage, resection status, perineural invasion (PNI), lymphovascular invasion (LVI), and degree of tumor differentiation. Compared with GBADC, GBNEC patients were younger (median age 56.0 vs 64.0 years; P = 0.001), and more patients presented with advanced stages of tumor (P = 0.003). Patients with GBNEC also had a higher rate of PNI (55.6% vs 22.4%; P < 0.001), and LVI (63.9% vs 45.80%; P = 0.658). Before PSM, GBNEC patients had inferior prognoses compared with GBADC patients with a shorter median overall survival (mOS) (15.02 vs 20.11 months; P = 0.0028) and a shorter median recurrence-free survival (mRFS) (10.30 vs 15.17 months; P = 0.0028). However, after PSM analyses, there were no differences in OS (mOS 18.6 vs 18.0 months; P=0.24) or RFS (mRFS 10.98 vs 12.02 months; P = 0.39) between the GBNEC and GBADC cases. After multivariate analysis, tumor diagnosis (GBNEC vs GBADC) was not identified as an independent risk factor for shorter RFS (P = 0.506) or OS (P = 0.731). Unfavorable pathological features, including advanced AJCC tumor stages, poor differentiation, presence of LVI, and positive resection margins (all P < 0.05), were independent risk factors for inferior OS and RFS. GBNEC is difficult to diagnose early and has a prognosis comparable to stage-matched poorly differentiated GBADC. Tumor diagnosis (either GBADC or GBNEC) was not an independent risk factor for the patient's OS. Unfavorable pathological features of the neoplasm are the main determinants.

Relation between WHO Classification and Location- and Functionality-Based Classifications of Neuroendocrine Neoplasms of the Digestive Tract

Practice of neuroendocrine neoplasms (NENs) of the digestive tract, which comprise of a highly diverse group of tumors with a rising incidence, faces multiple biological, diagnostic, and therapeutic issues. Part of these issues is due to misuse and misinterpretation of the classification and terminology of NENs of the digestive tract, which make it increasingly challenging to evaluate and compare the literature. For instance, grade 3 neuroendocrine tumors (NETs) are frequently referred to as neuroendocrine carcinomas (NECs) and vice versa, while NECs are, by definition, high grade and therefore constitute a separate entity from NETs. Moreover, the term NET is regularly misused to describe NENs in general, and NETs are frequently referred to as benign, while they should always be considered malignancies as they do have metastatic potential. To prevent misconceptions in future NEN-related research, we reviewed the most recent terminology used to classify NENs of the digestive tract and created an overview that combines the classification of these NENs according to the World Health Organization (WHO) with location- and functionality-based classifications. This overview may help clinicians and researchers in understanding the current literature and could serve as a guide in the clinic as well as for writing future studies on NENs of the digestive tract. In this way, we aim for the universal use of terminology, thereby providing an efficient foundation for future NEN-related research.

Case Report: Primary hepatic neuroendocrine tumor: two cases report with literature review

Background & Aims

Primary hepatic neuroendocrine tumors (PHNETs) are rare malignant liver tumors that present diagnostic challenges owing to their rarity and absence of specific clinical features. This study aimed to investigate the characteristics of this rare liver tumor to enhance our understanding of the disease, improve diagnostic accuracy, and explore standardized diagnostic and treatment approaches.

Case description

During physical examination, two elderly women, aged 64 and 74 years, were found to have liver masses. 18F-FDG Positron Emission Tomography-Computed Tomography (18F-FDG PET-CT) and Ga68-DOTATATE PET-CT scans of both individuals revealed multiple liver masses that were initially suspected to be hepatic neuroendocrine tumors. Subsequent puncture pathology confirmed the diagnosis of neuroendocrine tumors. Furthermore, in Case 1, the tumor was also detected by 18F-FDG PET-CT in the lung, suggesting a metastatic tumor, in conjunction with liver immunohistochemistry and imaging findings. Laboratory tests revealed no significant abnormalities in liver function or autoimmune liver disease indicators, and there was no evidence of viral hepatitis infection. However, partial hepatectomy was not indicated for cases with distant metastasis or multiple space-occupying lesions. Individualized treatment approaches have been developed for such situations. A large portion of the tumor underwent Transarterial Embolization (TAE), and targeted combination chemotherapy or endocrine therapy was administered based on the pathological results. During regular follow-ups a 13 and 12 months, the tumor remained stable. The patients' quality of life was good, and their psychological well-being was healthy. They led active lifestyles, demonstrated a thorough understanding of their disease and its progression, and actively cooperated during the follow-up process.

Conclusion

Our findings suggest that a combination of serological, radiological, and immunohistochemical examinations can aid in the diagnosis of PHNET. In addition, we determined that TAE combined with drug therapy could be an effective method for controlling PHNET progression. Regular postoperative follow-ups are important for monitoring the prognosis and tumor progression status of patients with PHNET.

Liver Transplant for Patients With Neuroendocrine Tumor: A Report of 2 Exceptional Cases and Literature Review

Patients with neuroendocrine tumors with unresec-table liver involvement can benefit from liver transplant. There is a specific set of guidelines for neuroendocrine tumors with liver metastasis that involve less than 50% of the liver. However, beyond those guidelines, there are reports of exceptional criteria patients who benefited from liver transplant. Here, we present 2 unusual cases of patients with exceptional circumstances and with neuroendocrine tumors who underwent liver transplant. The first case describes a patient with an extremely rare neuroen-docrine tumor of the proximal common bile duct that caused liver biliary cirrhosis. The patient underwent tumor resection and liver transplant concurrently. The second case describes a patient with a neuroendocrine tumor of unknown primary origin with more than 50% hepatic involvement who received a liver transplant after downstaging. In our center, patients with unresectable hepatic metastases from neuroendoc-rine tumors are currently selected for liver transplant based on well-established criteria. However, these 2 cases did not meet the criteria for consideration of liver transplant; thus, multidisciplinary team sessions were held to discuss these 2 cases. After a period of nonsurgical treatment and evaluation of the tumor behavior, we selected the patients as candidates for liver transplant based on the favorable tumor behavior and favorable response to treatment. For both patients, we did not observe any signs of tumor recurrence during follow-up. The outcomes were acceptable, and the patients tolerated treatment well. Considering the favorable tumor pathology (G1 phase and low Ki67 index), we suggest that more studies should be conducted to evaluate the outcomes of patients with low-grade tumors and that the criteria for patients with low-grade tumors could be extended based on such future data.

Primary extrahepatic biliary neuroendocrine tumor: a case report

Extrahepatic biliary neuroendocrine tumors (EBNETs) are extremely rare and difficult to diagnose. The vast majority are diagnosed postoperatively on histological evaluation of surgical specimens. Workup and treatment principles are largely based on retrospective series and case reports. Complete surgical resection is the gold standard treatment for these lesions. Here we present a case of a 77-year-old male with a biopsy-proven EBNET incidentally discovered during evaluation for fatty liver disease. Further workup did not show any other suspicious lesions. Resection of the tumor and multiple Roux-en-Y hepaticojejunostomy was performed. Final pathology revealed grade 1, well-differentiated neuroendocrine tumor. This is the third case reported in the literature with a confirmed preoperative EBNET diagnosis based on endoscopic biopsy results. This case highlights the feasibility of preoperative diagnosis of EBNETs and emphasizes the importance of complete surgical resection.

Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms of the Pancreas

Pancreatic mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) are rare neoplasms, composed of at least two components. The neuroendocrine part is always present. Histology is the most important tool for the diagnosis, but in the case of MiNEN, it is also important for the use of immunohistochemistry, which should include neuroendocrine but also ductal and acinar markers. Each component should be specifically described in the final pathology report, including the percentage on the entire tumor mass. The prognosis of MiNEN is very heterogeneous and depends on the different tumor components.

Overview of the 2022 WHO Classification of Neuroendocrine Neoplasms

In this review, we detail the changes and the relevant features that are applied to neuroendocrine neoplasms (NENs) in the 2022 WHO Classification of Endocrine and Neuroendocrine Tumors. Using a question-and-answer approach, we discuss the consolidation of the nomenclature that distinguishes neuronal paragangliomas from epithelial neoplasms, which are divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The criteria for these distinctions based on differentiation are outlined. NETs are generally (but not always) graded as G1, G2, and G3 based on proliferation, whereas NECs are by definition high grade; the importance of Ki67 as a tool for classification and grading is emphasized. The clinical relevance of proper classification is explained, and the importance of hormonal function is examined, including eutopic and ectopic hormone production. The tools available to pathologists for accurate classification include the conventional biomarkers of neuroendocrine lineage and differentiation, INSM1, synaptophysin, chromogranins, and somatostatin receptors (SSTRs), but also include transcription factors that can identify the site of origin of a metastatic lesion of unknown primary site, as well as hormones, enzymes, and keratins that play a role in functional and structural correlation. The recognition of highly proliferative, well-differentiated NETs has resulted in the need for biomarkers that can distinguish these G3 NETs from NECs, including stains to determine expression of SSTRs and those that can indicate the unique molecular pathogenetic alterations that underlie the distinction, for example, global loss of RB and aberrant p53 in pancreatic NECs compared with loss of ATRX, DAXX, and menin in pancreatic NETs. Other differential diagnoses are discussed with recommendations for biomarkers that can assist in correct classification, including the distinctions between epithelial and non-epithelial NENs that have allowed reclassification of epithelial NETs in the spine, in the duodenum, and in the middle ear; the first two may be composite tumors with neuronal and glial elements, and as this feature is integral to the duodenal lesion, it is now classified as composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). The many other aspects of differential diagnosis are detailed with recommendations for biomarkers that can distinguish NENs from non-neuroendocrine lesions that can mimic their morphology. The concepts of mixed neuroendocrine and non-neuroendocrine (MiNEN) and amphicrine tumors are clarified with information about how to approach such lesions in routine practice. Theranostic biomarkers that assist patient management are reviewed. Given the significant proportion of NENs that are associated with germline mutations that predispose to this disease, we explain the role of the pathologist in identifying precursor lesions and applying molecular immunohistochemistry to guide genetic testing.

Primary Hepatic Neuroendocrine Tumor: A Case Report and Literature Review

Primary hepatic neuroendocrine tumors (PHNETs) are an utterly rare subtype of neuroendocrine tumors (NETs) that arise from cells of the neuroendocrine system. Due to the rarity and lack of distinctive radiological features, diagnosis and management of this tumor are challenging. Herein, we report a case of PHNET in a 19-year-old previously healthy female patient whose diagnosis was confirmed by histopathology and immunohistochemistry. This case emphasizes the importance of considering PHNETs in the differential diagnosis of a hepatic mass, management of patients with this disease, and post-operative follow-up.

Primary hepatic neoplasms arising in cirrhotic livers can have a variable spectrum of neuroendocrine differentiation

Primary hepatic neoplasms with neuroendocrine differentiation are extremely rare. Their clinicopathological features and molecular genetic basis are largely unknown. We identified four cases of primary hepatic neoplasms with neuroendocrine differentiation. Electronic medical records were reviewed for clinical history, imaging findings, laboratory results, and follow-up. Pathology slides, immunohistochemistry, and ancillary studies were reviewed. There were two females and two males with age ranging from 52 to 74 years. There was one amphicrine carcinoma with tumor cells simultaneously demonstrating both hepatocellular and neuroendocrine differentiation, one mixed hepatocellular-neuroendocrine carcinoma (NEC) with hepatocellular component intermingled with neuroendocrine component, one small cell NEC, and one well-differentiated neuroendocrine tumor. Next- generation sequencing of the mixed hepatocellular-NEC and small cell NEC showed molecular/genetic alterations commonly seen in hepatocellular carcinoma (HCC). All four cases arose in a background of cirrhosis. Primary hepatic neoplasms arising in cirrhotic livers can have a spectrum of neuroendocrine differentiation. Presence of a NEC component may be an indicator of aggressiveness. In addition, primary hepatic carcinomas with neuroendocrine differentiation likely share the same molecular pathways as HCC.

Genomics of High-Grade Neuroendocrine Neoplasms: Well-Differentiated Neuroendocrine Tumor with High-Grade Features (G3 NET) and Neuroendocrine Carcinomas (NEC) of Various Anatomic Sites

High-grade neuroendocrine neoplasms (HG-NENs) are clinically aggressive diseases, the classification of which has recently been redefined. They now include both poorly differentiated NENs (neuroendocrine carcinoma, NECs) and high proliferating well-differentiated NENs (called grade 3 neuroendocrine tumors, G3 NETs, in the digestive system). In the last decade, the "molecular revolution" that has affected all fields of medical oncology has also shed light in the understanding of HG NENs heterogeneity and has provided new diagnostic and therapeutic tools, useful in the management of these malignancies. Considering the kaleidoscopic aspects of HG NENs in various anatomical sites, this review systematically addresses the genomic landscape of such neoplasm throughout the more common thoracic and digestive locations, as well as it will consider other rare but not exceptional primary sites, including the skin, the head and neck, and the urogenital system. The revision of the available literature will then be oriented to understand the translational relevance of molecular data, by analyzing conceptual issues, clinicopathological correlations, and unmet needs in this field.