Immunohistochemical distinction of paragangliomas from epithelial neuroendocrine tumors-gangliocytic duodenal and cauda equina paragangliomas align with epithelial neuroendocrine tumors

Hand2 Immunohistochemistry in the Diagnosis of Paragangliomas and Other Neuroendocrine Neoplasms

Hand2 is a core transcription factor responsible for chromaffin cell differentiation. However, its potential utility in surgical pathology has not been studied. Thus, we aimed to investigate its expression in paragangliomas, other neuroendocrine neoplasms (NENs), and additional non-neuroendocrine tumors. We calibrated Hand2 immunohistochemistry on adrenal medulla cells and analyzed H-scores in 46 paragangliomas (PGs), 9 metastatic PGs, 21 cauda equina neuroendocrine tumors (CENETs), 48 neuroendocrine carcinomas (NECs), 8 olfactory neuroblastomas (ONBs), 110 well-differentiated NETs (WDNETs), 10 adrenal cortical carcinomas, 29 adrenal cortical adenomas, 8 melanomas, 41 different carcinomas, and 10 gastrointestinal stromal tumors (GISTs). Both tissue microarrays (TMAs) and whole sections (WSs) were studied. In 171 NENs, previously published data on Phox2B and GATA3 were correlated with Hand2. Hand2 was positive in 98.1% (54/55) PGs, but only rarely in WDNETs (9.6%, 10/104), CENETs (9.5%, 2/21), NECs (4.2%, 2/48), or ONBs (12.5%, 1/8). Any Hand2 positivity was 98.1% sensitive and 91.7% specific for the diagnosis of PG. The Hand2 H-score was significantly higher in primary PGs compared to Hand2-positive WDNETs (median 166.3 vs. 7.5; p < 0.0001). Metastatic PGs were positive in 88.9% (8/9). No Hand2 positivity was observed in any adrenal cortical neoplasm or other non-neuroendocrine tumors, with exception of 8/10 GISTs. Parasympathetic PGs showed a higher Hand2 H-score compared to sympathetic PGs (median H-scores 280 vs. 104, p < 0.0001). Hand2 positivity in NENs serves as a reliable marker of primary and metastatic PG, since other NENs only rarely exhibit limited Hand2 positivity.

S100 Protein Expression in Primary and Metastatic Neuroendocrine Neoplasms: A Specific Marker of Pancreatic Origin

Neuroendocrine neoplasms can arise in a wide variety of anatomic sites including the gastrointestinal tract, pancreas, and lung, among others. Here, we report on the expression of S100 protein in a tissue microarray composed of 919 distinct primary and metastatic neuroendocrine neoplasms from 548 patients. S100 protein is a commonly used marker in many laboratories for the identification of neural and melanocytic neoplasms and occasionally used in the workup for neuroendocrine neoplasms when the diagnosis of paraganglioma is being considered. We show that strong S100 protein expression is highly specific to well-differentiated neuroendocrine tumors of pancreatic origin. This finding suggests potential diagnostic utility of this marker in cases of tumors of unknown origin, and emphasizes that S100 protein expression should not be an unexpected finding in neuroendocrine tumors of pancreatic origin.

[Exocrine meets neuroendocrine: mimickers of pancreatic neuroendocrine neoplasms]

Neuroendocrine neoplasms (NENs) originate from various epithelial or neuroectodermal tissues, can occur in any organ, including the pancreas, and are characterized by the expression of the neuroendocrine markers synaptophysin and chromogranin A. Pancreatic neuroendocrine tumors (PanNETs) are well-differentiated epithelial neoplasms with morphological and immunohistochemical features of neuroendocrine differentiation of low, intermediate, or high grade. Pancreatic neuroendocrine carcinomas (PanNECs) are clinically aggressive, high-grade (poorly differentiated) carcinomas with morphologic features suggesting neuroendocrine differentiation, a high proliferative rate (> 20 mitoses per 2 mm2 and Ki67 index > 20%), and immunohistochemical labeling for neuroendocrine markers. They include the small cell neuroendocrine carcinoma and the large cell neuroendocrine carcinoma categories.Neuroendocrine-like morphology coupled with immunohistochemical markers of neuroendocrine differentiation are highly specific. However, neuroendocrine markers may also be expressed in non-neuroendocrine neoplasms, which can therefore be confused with NENs. Mimickers of pancreatic NENs comprise a number of important pitfall tumors, including epithelial and non-epithelial neoplasms, such as acinar cell carcinomas, solid pseudopapillary neoplasms (SPNs), or even non-neoplastic lesions. All of these lesions have the expression of neuroendocrine markers in common, such as synaptophysin and chromogranin A, and although they are comparatively rare, they can cause considerable diagnostic problems. This review article deals with some of the most important mimickers of pancreatic neuroendocrine neoplasms and even non-neoplastic lesions, such as islet aggregation. The similarities and differences between these entities and pancreatic neuroendocrine neoplasms are highlighted, and key findings that facilitate the correct diagnosis are discussed.

European Neuroendocrine Tumor Society (ENETS) 2023 guidance paper for gastroduodenal neuroendocrine tumours (NETs) G1-G3

The aim of the present guidance paper was to update the previous ENETS guidelines on well-differentiated gastric and duodenal neuroendocrine tumours (NETs), providing practical guidance for specialists in the diagnosis and management of gastroduodenal NETs. Type II gastric NETs, neuroendocrine carcinomas (NECs), and functioning duodenal NETs are not covered, since they will be discussed in other ENETS guidance papers.

SDH-B, INSM1, and GATA3 expression in cauda equina neuroendocrine tumors: Report on 21 cases from a north Indian tertiary care centre

BACKGROUND

Primary neuroendocrine tumors (NETs) of the central nervous system (CNS) are rare, primarily seen in the cauda equina region, known as cauda equina NETs. This study was carried out to evaluate the morphological and immunohistochemical characteristics of cauda equina NETs.

MATERIAL AND METHODS

All cases of histologically proven NETs that originated within the spinal cord from 2010 to 2021 were retrieved from the surgical pathology electronic database. For each case, the clinical presentation, site, radiological features, functional status, and pre-operative diagnosis were recorded. Immunohistochemical stains for GFAP, synaptophysin, chromogranin A, cytokeratin 8/18, INSM-1, Ki67, GATA3, and SDH-B were performed for every case using automated immunostainer. GATA3 immunohistochemistry was repeated manually.

RESULTS

A retrospective probe of records revealed 21 cases of NETs having a mean age of 44 years and slight male dominance (M:F ratio 1.2:1). Cauda equina was the most prevalent site of involvement (19, 90.5%). The most typical presentation was lower backache and weakness of bilateral lower limbs. The histopathological features were similar to NETs seen at other sites. Reactivity for at least one neuroendocrine marker was seen in all cases while GFAP was negative. Cytokeratin 8/18 was expressed in the majority (88.9%) of cases. INSM1 and GATA3 expression was seen in 20 (95.2%) and 3 (14.3%) cases, respectively. All cases retained SDH-B cytoplasmic staining. Higher Ki67 index (>3%) was associated with higher risk of recurrence.

CONCLUSIONS

Cauda equina NETs rarely express GATA3 and are unlikely to be associated with SDH mutations. Recurrent cases may be negative for synaptophysin, chromogranin, and cytokeratin; thus INSM1 IHC is helpful.

Cauda Equina Neuroendocrine Tumors: Distinct Epithelial Neuroendocrine Neoplasms of Spinal Origin

The tumor formerly known as "cauda equina paraganglioma" was recently renamed as cauda equina neuroendocrine tumor (CENET) based on distinct biological and genetic properties. Nevertheless, it remains insufficiently understood. For this study, we retrieved CENETs (some previously reported), from the pathology files of 3 institutions; we examined their immunohistochemical profile, including common neuroendocrine tumor-associated hormones and transcription factors. We identified 24 CENETs from 7 female and 17 male adult patients, with a median age of 47 years. Six included neurofilament-positive ganglion cells. All tumors tested were positive for INSM1, synaptophysin, chromogranin A, SSTR2, and CD56 as well as at least 1 keratin (AE1/AE3, CAM5.2); CK7 and CK20 were negative. Glial fibrillary acidic protein was negative, except for peripheral nontumoral elements. S100 protein was variable but mainly expressed in scattered sustentacular cells. All but 1 tumor tested were positive for HOXB13; several stained for SATB2, and all tumors were consistently negative for GATA3. All tumors tested were negative for transcription factors found in various other epithelial neuroendocrine neoplasms including TTF1, CDX2, PIT1, TPIT, SF1, and PAX8; staining for T-brachyury was negative. Four of 5 CENETs tested had at least focal tyrosine hydroxylase reactivity. Serotonin expression was detected in all 21 tumors tested; it was diffusely positive in 5 and had variable positivity in the remainder. A few tumors had scattered cells expressing gastrin, calcitonin, pancreatic polypeptide, and peptide YY, while glucagon, adrenocorticotropic hormone, and monoclonal carcinoembryonic antigen were negative. PSAP expression was found focally in 4 of 5 tumors examined. SDHB was consistently intact; ATRX was intact in 14 tumors and showed only focal loss in 3. The median Ki-67 labeling index was 4.5% (range: 1% to 15%). We conclude that CENET represents a distinct neuroendocrine neoplasm; the subset with ganglion cells qualifies for designation as composite gangliocytoma/neuroma-neuroendocrine tumor (CoGNET) as defined in the 2022 WHO classification of neuroendocrine neoplasms. In addition to INSM1, chromogranin, synaptophysin, and keratins, the most characteristic finding is nuclear HOXB13 expression; a subset also express SATB2. Serotonin is the most common hormone expressed. The cytogenesis and pathogenesis of these lesions remains unclear.

Top 10 Nested Pattern Head and Neck Lesions to Notice

BACKGROUND

Nested is defined as "cellular clusters arranged in small groupings with intervening vascular or stromal networks, lacking lumens or glandular formation." Using this definition, multiple neoplastic and non-neoplastic lesions of the head and neck come into the differential. We have broadly organized the differential diagnosis of "nested" tumors into entities with neuroendocrine differentiation, squamous differentiation, thyroid follicular cell differentiation, and other lesions.

METHODS

Review.

RESULTS

Many different entities have a nested appearance and the morphologic, immunohistochemical, clinical, and radiographic features contribute to the differential diagnosis. The different tumors covered in this review include neuroendocrine neoplasms, paraganglioma, middle ear neuroendocrine tumor (formerly known as middle ear adenoma), medullary thyroid carcinoma, poorly differentiated thyroid carcinoma, olfactory neuroblastoma, ectopic pituitary neuroendocrine tumor, hyalinizing trabecular tumor, solid subtype of papillary thyroid carcinoma, solid cell nests/C-cell hyperplasia, necrotizing sialometaplasia, and meningioma.

CONCLUSION

In this review, we discuss the morphologic and immunohistochemical features of the covered entities as a guide to differential diagnosis when nested-patterned head and neck lesions are encountered.

Cauda equina neuroendocrine tumors show biological features distinct from other paragangliomas and visceral neuroendocrine tumors

Cauda equina neuroendocrine tumors (CENETs) are neoplasms of uncertain histogenesis with overlapping features between those of paragangliomas (PGs) and visceral neuroendocrine tumors (NETs). We have explored their biological relationship to both subsets of neuroendocrine neoplasms. The clinical and radiological features of a cohort of 23 CENETs were analyzed. A total of 21 cases were included in tissue microarrays, along with a control group of 38 PGs and 83 NETs. An extensive panel of antibodies was used to assess epithelial phenotype (cytokeratins, E-cadherin, EpCAM, Claudin-4, EMA, CD138), neuronal and neuroendocrine features (synaptophysin, chromogranin A, INSM1, neurofilaments, NeuN, internexin-α, calretinin), chromaffin differentiation (GATA3, Phox2b, tyrosine hydroxylase), and possible histogenesis (Sox2, T-brachyury, Oct3/4, Sox10). The cohort included 5 women (22%) and 18 men (78%). The average age at the time of surgery was 48.3 years (range from 21 to 80 years). The average diameter of the tumors was 39.27 mm, and invasion of surrounding structures was observed in 6/21 (29%) tumors. Follow-up was available in 16 patients (median 46.5 months). One tumor recurred after 19 months. No metastatic behavior and no endocrine activity were observed. Compared to control groups, CENETs lacked expression of epithelial adhesion molecules (EpCAM, CD138, E-cadherin, Claudin-4), and at the same time, they lacked features of chromaffin differentiation (GATA3, Phox2b, tyrosine hydroxylase). We observed no loss of SDHB. Cytokeratin expression was present in all CENETs. All the CENETs showed variable cytoplasmic expression of T-brachyury and limited nuclear expression of Sox2. These findings support the unique nature of the neoplasm with respect to NETs and PGs.

Phox2B is a sensitive and reliable marker of paraganglioma-Phox2B immunohistochemistry in diagnosis of neuroendocrine neoplasms

Phox2B is a transcription factor responsible for chromaffin cell phenotype. Although it is used routinely for diagnosis of neuroblastoma, previous reports concerning its utility in the diagnosis of neuroendocrine neoplasms have been conflicting. We assessed Phox2b immunoreactivity in different neuroendocrine neoplasms. Tissue microarrays or whole sections of 36 paragangliomas (PGs), 91 well-differentiated neuroendocrine tumours of different organs (WDNETs), 31 neuroendocrine carcinomas (NECs), and 6 olfactory neuroblastomas (ONBs) were stained with Phox2B antibody (EP312) and GATA3. The percentage of positive cells and intensity was analysed using H-score. Phox2B immunoreactivity was seen in 97.2% (35/36) PGs, 11% (10/91) WDNETs, 9.7% (3/31) NECs, and 16.7% (1/6) ONBs. PGs were significantly more often positive (p < 0.001, χ²) than other neuroendocrine tumours, showing highest H-score (mean 144.9, SD ± 75.1) and percentage of positive cells (median 81.3%, IQR 62.5-92.5%). Compared to Phox2B-positive WDNETs, PGs showed significantly higher H-score (median 145 vs 7.5, p < 0.001) and percentage of positive cells (median 82.5% vs 4.5%, p < 0.001). Phox2B positivity was 97.2% sensitive and 89% specific for the diagnosis of PG. GATA3 was 100% sensitive and 88% specific for the diagnosis of PG. When combined, any Phox2B/GATA3 coexpression was 97.1% sensitive and 99.1% specific for the diagnosis of paraganglioma. Widespread Phox2B immunoreactivity is a highly characteristic feature of PGs and it can be used as an additional marker in differential diagnosis of neuroendocrine tumours.

Neuroendocrine Neoplasms of the Pancreas: Diagnostic Challenges and Practical Approach

Most pancreatic neuroendocrine neoplasms are slow-growing, and the patients may survive for many years, even after distant metastasis. The tumors usually display characteristic organoid growth patterns with typical neuroendocrine morphology. A smaller portion of the tumors follows a more precipitous clinical course. The classification has evolved from morphologic patterns to the current World Health Organization classification, with better-defined grading and prognostic criteria. Recent advances in molecular pathology have further improved our understanding of the pathogenesis of these tumors. Various issues and challenges remain, including the correct recognition of a neuroendocrine neoplasm, accurate classification and grading of the tumor, and differentiation from mimickers. This review focuses on the practical aspects during the workup of pancreatic neuroendocrine neoplasms and attempts to provide a general framework to help achieve an accurate diagnosis, classification, and grading.

PHOX2B is a Sensitive and Specific Marker for the Histopathological Diagnosis of Pheochromocytoma and Paraganglioma

Pheochromocytomas (PCCs) and paragangliomas (PGLs) are non-epithelial neuroendocrine neoplasms originating from the adrenal medulla and paraganglion of the sympathetic and parasympathetic nervous system, respectively. PCCs and PGLs show histological similarities with other epithelial neuroendocrine neoplasms and olfactory neuroblastomas (ONBs), and the differential diagnosis of PGLs is particularly difficult. Therefore, we compared the sensitivity of PHOX2A, PHOX2B, and tyrosine hydroxylase (TH) in the histopathological diagnosis of PCCs and PGLs immunohistochemically using the tissue microarrays of 297 neoplasms including PCCs, PGLs, neuroblastomas, ganglioneuromas, epithelial neuroendocrine neoplasms, and ONBs. Using cutoff values of 25%, 5%, and 5% of tumor cells expressing PHOX2A, PHOX2B, and TH, respectively, as positive, 40 of 51 PCCs, 32 of 33 parasympathetic/head and neck PGLs (HNPGLs), 17 of 19 sympathetic/thoracoabdominal PGLs (TAPGLs), and 12 of 152 epithelial neuroendocrine neoplasms, including 123 well-differentiated and 29 poorly differentiated neuroendocrine neoplasms, were PHOX2A-positive. All 51 PCCs, 33 HNPGLs, and 19 TAPGLs were PHOX2B-positive, while all 152 epithelial neuroendocrine neoplasms were PHOX2B-negative. Moreover, 50 of 51 PCCs, 13 of 33 HNPGLs, all TAPGLs, and 12 of 152 epithelial neuroendocrine neoplasms were TH-positive. All ONBs were negative for PHOX2A, PHOX2B, and TH. PHOX2B was the most sensitive and specific diagnostic marker for PCCs and PGLs among PHOX2A, PHOX2B, and TH. PHOX2B can facilitate identification of PCCs and PGLs from epithelial neuroendocrine neoplasms and ONBs, especially in the case of HNPGLs, in which TH is often negative.

A case report of primary colonic paraganglioma with lymph node metastasis

Background

Paraganglioma is a kind of neuroendocrine tumor that originates from paraganglia outside the adrenal gland. Gastrointestinal tract paraganglioma is very rare and only four cases of paraganglioma originating in the colon have been reported.

Case Presentation

We report a case of metastatic paraganglioma originating in the colon, in which the differential diagnosis was established by comprehensively considering clinical information, histology, immunohistochemistry, and findings of fluorescence in situ hybridization and next generation sequencing analyses. The patient has remained well for over 14 months after the treatment.

Conclusion

Since all paraganglioma have metastatic potential, we believe that radical surgical resection and regular follow-up are necessary. Genetic testing may be indicative of metastatic potential and prognosis. Because colonic paraganglioma is very rare, differential diagnosis is very important. Our report provides experience for the diagnosis and study of paraganglioma in rare sites.

Preoperative Diagnosis of Abdominal Extra-Adrenal Paragangliomas with Fine-Needle Biopsy

Paragangliomas are rare, non-epithelial neuroendocrine neoplasms originating in paraganglia, for instance the adrenal medulla, or at extra-adrenal locations. The aim of this study was to review the literature regarding abdominal extra-adrenal paragangliomas diagnosed pre-operatively with fine-needle biopsy (FNA and/or FNB). The PubMed database was searched to identify such cases, using a specific algorithm and inclusion/exclusion criteria. An unpublished case from our practice was also added to the rest of the data, resulting in a total of 36 cases for analysis. Overall, 24 (67%) lesions were found in females, whereas 12 (33%) in males. Most (21/36; 58.33%) were identified around and/or within the pancreatic parenchyma. FNA and/or FNB reached or suggested a paraganglioma diagnosis in 17/36 cases (47.22%). Of the preoperative misdiagnoses, the most common was an epithelial neuroendocrine tumor (NET). Regarding follow-up, most patients were alive with no reported recurrence; however, 5/36 patients exhibited a recurrence or a widespread disease, whereas one patient died 48 months following her diagnosis. In two patients, transient hypertension was reported during the EUS-FNA procedure. In conclusion, this study showed that the preoperative diagnosis of these lesions is feasible and, while diagnostic pitfalls exist, they could significantly be avoided with the application of immunochemistry.

Cervical Small Cell Variant of Paraganglioma With Sarcomatous Transformation: Report of a Unique Case

We report a unique primary cervical neoplasm in a 44-yr-old woman which we believe, based on the morphology and immunophenotype, represents an extremely unusual small cell variant of paraganglioma. This represents the first report of a primary cervical paraganglioma. Following chemoradiation treatment, the tumor underwent malignant transformation into an S100 and SOX10 positive sarcoma, morphologically and immunohistochemically resembling a malignant peripheral nerve sheath tumor, which we believe represents a sarcoma derived from the sustentacular cells of the paraganglioma. Mutational analysis detected a nonsense mutation of NF1 gene in the sarcoma. This further supports the diagnosis as both somatic and germline NF1 mutations have been associated with paragangliomas and malignant peripheral nerve sheath tumors. Targeted RNA sequencing (ARCHER, expanded sarcoma panel) covering many known genes implicated in sarcoma development, did not reveal any other molecular alteration (fusion or internal tandem duplication).

Clinicopathological and Molecular Features of Secondary Cancer (Metastasis) to the Thyroid and Advances in Management

Secondary tumours to the thyroid gland are uncommon and often incidentally discovered on imaging. Symptomatic patients often present with a neck mass. Collision tumours of secondary tumours and primary thyroid neoplasms do occur. Ultrasound-guided fine-needle aspiration, core-needle biopsy, and surgical resection with histological and immunohistochemical analysis are employed to confirm diagnosis as well as for applying molecular studies to identify candidates for targeted therapy. Biopsy at the metastatic site can identify mutations (such as EGFR, K-Ras, VHL) and translocations (such as EML4-ALK fusion) important in planning target therapies. Patients with advanced-stage primary cancers, widespread dissemination, or unknown primary origin often have a poor prognosis. Those with isolated metastasis to the thyroid have better survival outcomes and are more likely to undergo thyroid resection. Systemic therapies, such as chemotherapy and hormonal therapy, are often used as adjuvant treatment post-operatively or in patients with disseminated disease. New targeted therapies, such as tyrosine kinase inhibitors and immune checkpoint inhibitors, have shown success in reported cases. A tailored treatment plan based on primary tumour features, overall cancer burden, and co-morbidities is imperative. To conclude, secondary cancer to the thyroid is uncommon, and awareness of the updates on diagnosis and management is needed.

An update on the development of concepts, diagnostic criteria, and challenging issues for neuroendocrine neoplasms across different digestive organs

Digestive neuroendocrine neoplasms (NENs) are a group of heterogeneous neoplasms found throughout the digestive tract, with different behaviour and genetic background. In the last few years, nomenclature and WHO/UICC classifications of digestive NENs have changed, and molecular classifications have emerged, especially in pancreatic locations. Increasing patho-molecular details are needed to diagnose the different categories of NEN, including the use of helpful immunohistochemical markers. In this review, we address these topics in three successive chapters. We first briefly review recent updates in classifications, discuss important grading and proliferating issues and advances in the molecular understanding of NEN. Then, we provide an update on diagnosis, including the most important differential diagnoses of NEN, with a focus on high-grade neoplasms and mixed tumours. Finally, we highlight a variety of currently used and next-generation predictive and prognostic biomarkers as well as biomarkers of tumour origin and describe some site specificities of gastrointestinal NEN. We specifically focus on biomarkers available to pathologists with the potential to change the way patients with NEN are diagnosed and treated.

Overview of the 2022 WHO Classification of Paragangliomas and Pheochromocytomas

This review summarizes the classification of tumors of the adrenal medulla and extra-adrenal paraganglia as outlined in the 5th series of the WHO Classification of Endocrine and Neuroendocrine Tumors. The non-epithelial neuroendocrine neoplasms (NENs) known as paragangliomas produce predominantly catecholamines and secrete them into the bloodstream like hormones, and they represent a group of NENs that have exceptionally high genetic predisposition. This classification discusses the embryologic derivation of the cells that give rise to these lesions and the historical evolution of the terminology used to classify their tumors; paragangliomas can be sympathetic or parasympathetic and the term pheochromocytoma is used specifically for intra-adrenal paragangliomas that represent the classical sympathetic form. In addition to the general neuroendocrine cell biomarkers INSM1, synaptophysin, and chromogranins, these tumors are typically negative for keratins and instead have highly specific biomarkers, including the GATA3 transcription factor and enzymes involved in catecholamine biosynthesis: tyrosine hydroxylase that converts L-tyrosine to L-DOPA as the rate-limiting step in catecholamine biosynthesis, dopamine beta-hydroxylase that is present in cells expressing norepinephrine, and phenylethanolamine N-methyltransferase, which converts norepinephrine to epinephrine and therefore can be used to distinguish tumors that make epinephrine. In addition to these important tools that can be used to confirm the diagnosis of a paraganglioma, new tools are recommended to determine genetic predisposition syndromes; in addition to the identification of precursor lesions, molecular immunohistochemistry can serve to identify associations with SDHx, VHL, FH, MAX, and MEN1 mutations, as well as pseudohypoxia-related pathogenesis. Paragangliomas have a well-formed network of sustentacular cells that express SOX10 and S100, but this is not a distinctive feature, as other epithelial NENs also have sustentacular cells. Indeed, it is the presence of such cells and the association with ganglion cells that led to a misinterpretation of several unusual lesions as paragangliomas; in the 2022 WHO classification, the tumor formerly known as cauda equina paraganglioma is now classified as cauda equina neuroendocrine tumor and the lesion known as gangliocytic paraganglioma has been renamed composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). Since the 4th edition of the WHO, paragangliomas have no longer been classified as benign and malignant, as any lesion can have metastatic potential and there are no clear-cut features that can predict metastatic behavior. Moreover, some tumors are lethal without metastatic spread, by nature of local invasion involving critical structures. Nevertheless, there are features that can be used to identify more aggressive lesions; the WHO does not endorse the various scoring systems that are reviewed but also does not discourage their use. The identification of metastases is also complex, particularly in patients with germline predisposition syndromes, since multiple lesions may represent multifocal primary tumors rather than metastatic spread; the identification of paragangliomas in unusual locations such as lung or liver is not diagnostic of metastasis, since these may be primary sites. The value of sustentacular cells and Ki67 labeling as prognostic features is also discussed in this new classification. A staging system for pheochromocytoma and extra-adrenal sympathetic PGLs, introduced in the 8th Edition AJCC Cancer Staging Manual, is now included. This paper also provides a summary of the criteria for the diagnosis of a composite paragangliomas and summarizes the classification of neuroblastic tumors. This review adopts a practical question-answer framework to provide members of the multidisciplinary endocrine oncology team with a most up-to-date approach to tumors of the adrenal medulla and extra-adrenal paraganglia.

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.

Challenges in Paragangliomas and Pheochromocytomas: from Histology to Molecular Immunohistochemistry

Abdominal paragangliomas and pheochromocytomas (PPGLs) are rare neuroendocrine tumors of the infradiaphragmatic paraganglia and adrenal medulla, respectively. Although few pathologists outside of endocrine tertiary centers will ever diagnose such a lesion, the tumors are well known through the medical community-possible due to a combination of the sheer rarity, their often-spectacular presentation due to excess catecholamine secretion as well as their unrivaled coupling to constitutional susceptibility gene mutations and hereditary syndromes. All PPGLs are thought to harbor malignant potential, and therefore pose several challenges to the practicing pathologist. Specifically, a responsible diagnostician should recognize both the capacity and limitations of histological, immunohistochemical, and molecular algorithms to pinpoint high risk for future metastatic disease. This focused review aims to provide the surgical pathologist with a condensed update regarding the current strategies available in order to deliver an accurate prognostication of these enigmatic lesions.

Laparoscopic resection of a paraganglioma in the greater omentum mimicking a peripancreatic neoplasm: a case report

A paraganglioma is a tumor originating in the sympathetic or parasympathetic nervous system. Its diagnosis may sometimes be confusing if it occurs in an atypical site. We described herein a case of a peripancreatic paraganglioma originating in the greater omentum. An asymptomatic, 61-year-old, female patient was referred to our hospital for detailed examination of a peripancreatic mass detected incidentally on computed tomography (CT). The differential diagnosis was a neuroendocrine neoplasm (NEN), and a biopsy using EUS-FNA was performed. Histologically, the tumor cells showed proliferation in solid cell nests and were positive for CD56, chromogranin A, and synaptophysin. These findings and the hypervascularity of the tumor on imaging studies were compatible with NEN. Since the imaging studies did not clearly demonstrate the continuity of the tumor with the pancreas, laparoscopic tumor resection without a pancreatectomy and sampling of the enlarged peripancreatic lymph nodes were planned as treatment. The absence of continuity with the pancreas was later confirmed by intraoperative observation, and the resection was carried out as planned. The resected tumor was pathologically considered as NEN at first in agreement with the preoperative diagnosis. However, several histological findings (such as a zelleballen-like growth pattern, pseudo-inclusion, and strong nuclear atypia compared with the cells' proliferative ability) were atypical for NEN, and paraganglioma was included in the differential diagnosis. Additional immunostainings of S-100 and AE1/AE3 were performed, leading to the final diagnosis of paraganglioma. Paragangliomas should be included in the differential diagnosis of an intraperitoneal mass of uncertain identity with hypervascularity.

Metastatic Pheochromocytomas and Abdominal Paragangliomas

CONTEXT

Pheochromocytomas and paragangliomas (PPGLs) are believed to harbor malignant potential; about 10% to 15% of pheochromocytomas and up to 50% of abdominal paragangliomas will exhibit metastatic behavior.

EVIDENCE ACQUISITION

Extensive searches in the PubMed database with various combinations of the key words pheochromocytoma, paraganglioma, metastatic, malignant, diagnosis, pathology, genetic, and treatment were the basis for the present review.

DATA SYNTHESIS

To pinpoint metastatic potential in PPGLs is difficult, but nevertheless crucial for the individual patient to receive tailor-made follow-up and adjuvant treatment following primary surgery. A combination of histological workup and molecular predictive markers can possibly aid the clinicians in this aspect. Most patients with PPGLs have localized disease and may be cured by surgery. Plasma metanephrines are the main biochemical tests. Genetic testing is important, both for counseling and prognostic estimation. Apart from computed tomography and magnetic resonance imaging, molecular imaging using 68Ga-DOTATOC/DOTATATE should be performed. 123I-MIBG scintigraphy may be performed to determine whether 131I-MIBG therapy is a possible option. As first-line treatment in patients with metastatic disease, 177Lu-DOTATATE or 131I-MIBG is recommended, depending on which shows best expression. In patients with very low proliferative activity, watch-and-wait or primary treatment with long-acting somatostatin analogues may be considered. As second-line treatment, or first-line in patients with high proliferative rate, chemotherapy with temozolomide or cyclophosphamide + vincristine + dacarbazine is the therapy of choice. Other therapies, including sunitinib, cabozantinib, everolimus, and PD-1/PDL-1 inhibitors, have shown modest effect.

CONCLUSIONS

Metastatic PPGLs need individualized management and should always be discussed in specialized and interdisciplinary tumor boards. Further studies and newer treatment modalities are urgently needed.

Neuroendocrine neoplasms of the duodenum, ampullary region, jejunum and ileum

Neuroendocrine neoplasms of the small intestine are some of the most frequently occurring along the gastrointestinal tract, even though their incidence is extremely variable according to specific sites. Jejunal-ileal neuroendocrine neoplasms account for about 27% of gastrointestinal NETs making them the second most frequent NET type. The aim of this review is to classify all tumors following the WHO 2019 classification and to describe their pathologic differences and peculiarities.

The immunohistochemical, DNA methylation, and chromosomal copy number profile of cauda equina paraganglioma is distinct from extra-spinal paraganglioma

Paragangliomas are neuroendocrine tumors of the autonomic nervous system that are variably clinically functional and have a potential for metastasis. Up to 40% occur in the setting of a hereditary syndrome, most commonly due to germline mutations in succinate dehydrogenase (SDHx) genes. Immunohistochemically, paragangliomas are characteristically GATA3-positive and cytokeratin-negative, with loss of SDHB expression in most hereditary cases. In contrast, the rare paragangliomas arising in the cauda equina (CEP) or filum terminale region have been shown to be hormonally silent, clinically indolent, and have variable keratin expression, suggesting these tumors may represent a separate pathologic entity. We retrospectively evaluated 17 CEPs from 11 male and 6 female patients with a median age of 38 years (range 21-82), none with a family history of neuroendocrine neoplasia. Six of the 17 tumors demonstrated prominent gangliocytic or ganglioneuromatous differentiation. By immunohistochemistry, none of the CEPs showed GATA3 positivity or loss of SDHB staining; all 17 CEPs were cytokeratin positive. Genome-wide DNA methylation profiling was performed on 12 of the tumors and compared with publicly available genome-wide DNA methylation data. Clustering analysis showed that CEPs form a distinct epigenetic group, separate from paragangliomas of extraspinal sites, pheochromocytomas, and other neuroendocrine neoplasms. Copy number analysis revealed diploid genomes in the vast majority of CEPs, whereas extraspinal paragangliomas were mostly aneuploid with recurrent trisomy 1q and monosomies of 1p, 3, and 11, none of which were present in the cohort of CEP. Together, these findings indicate that CEPs likely represent a distinct entity. Future genomic studies are needed to further elucidate the molecular pathogenesis of these tumors.

Molecular characterization of CNS paragangliomas identifies cauda equina paragangliomas as a distinct tumor entity

Paragangliomas/pheochromocytomas are rare neuroendocrine tumors that arise from the adrenal gland or ganglia at various sites throughout the body. They display a remarkable diversity of driver alterations and are associated with germline mutations in up to 40% of the cases. Comprehensive molecular profiling of abdomino-thoracic paragangliomas revealed four molecularly defined and clinically relevant subtypes. Paragangliomas of the cauda equina region are considered to belong to one of the defined molecular subtypes, but a systematic molecular analysis has not yet been performed. In this study, we analyzed genome-wide DNA methylation profiles of 57 cauda equina paragangliomas and show that these tumors are epigenetically distinct from non-spinal paragangliomas and other tumors. In contrast to paragangliomas of other sites, chromosomal imbalances are widely lacking in cauda equina paragangliomas. Furthermore, RNA and DNA exome sequencing revealed that frequent genetic alterations found in non-spinal paragangliomas—including the prognostically relevant SDH mutations—are absent in cauda equina paragangliomas. Histologically, cauda equina paragangliomas show frequently gangliocytic differentiation and strong immunoreactivity to pan-cytokeratin and cytokeratin 18, which is not common in paragangliomas of other sites. None of our cases had a familial paraganglioma syndrome. Tumors rarely recurred (9%) or presented with multiple lesions within the spinal compartment (7%), but did not metastasize outside the CNS. In summary, we show that cauda equina paragangliomas represent a distinct, sporadic tumor entity defined by a unique clinical and morpho-molecular profile.