SATB2 in neuroendocrine neoplasms: strong expression is restricted to well-differentiated tumours of lower gastrointestinal tract origin and is most frequent in Merkel cell carcinoma among poorly differentiated carcinomas

Anal carcinoma - exploring the epidemiology, risk factors, pathophysiology, diagnosis, and treatment

Anal carcinoma is a relatively rare tumor that accounts for approximately 2% of gastrointestinal malignancies and less than 7% of anorectal cancers. Most anal tumors originate between the anorectal junction and the anal verge. Risk factors for the disease include human papillomavirus infection, human immunodeficiency virus, tobacco use, immunosuppression, female sex, and older age. The pathogenesis of anal carcinoma is believed to be linked to human papillomavirus-related inflammation, leading to dysplasia and progression to cancer. Squamous cell carcinoma is the most common type of anal tumor, with an annual incidence of approximately 1 to 2 per 100000 persons. Treatment regarding anal cancer has emerged over time. However, chemoradiation therapy remains the mainstay approach for early localized disease. Patients with metastatic disease are treated with systemic therapy, and salvage surgery is reserved for disease recurrence following chemoradiation. This article aims to provide background information on the epidemiology, risk factors, pathology, diagnosis, and current trends in the management of anal cancer. Future directions are briefly discussed.

Merkel cell carcinoma: updates in tumor biology, emerging therapies, and preclinical models

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma thought to arise via either viral (Merkel cell polyomavirus) or ultraviolet-associated pathways. Surgery and radiotherapy have historically been mainstays of management, and immunotherapy has improved outcomes for advanced disease. However, there remains a lack of effective therapy for those patients who fail to respond to these established approaches, underscoring a critical need to better understand MCC biology for more effective prognosis and treatment. Here, we review the fundamental aspects of MCC biology and the recent advances which have had profound impact on management. The first genetically-engineered mouse models for MCC tumorigenesis provide opportunities to understand the potential MCC cell of origin and may prove useful for preclinical investigation of novel therapeutics. The MCC cell of origin debate has also been advanced by recent observations of MCC arising in association with a clonally related hair follicle tumor or squamous cell carcinoma in situ. These studies also suggested a role for epigenetics in the origin of MCC, highlighting a potential utility for this therapeutic avenue in MCC. These and other therapeutic targets form the basis for a wealth of ongoing clinical trials to improve MCC management. Here, we review these recent advances in the context of the existing literature and implications for future investigations.

PCSK2 can be Useful in a Panel Approach to Distinguish Foregut and Midgut Neuroendocrine Tumors

A number of immunohistochemical stains have been examined for utility in establishing the site of origin for metastatic well-differentiated neuroendocrine tumors (NETs). In the gastrointestinal (GI) tract, distinguishing metastatic duodenal NETs from jejunoileal and other GI NETs is important for clinical work-up, prognosis, and therapy. A recent study indicated that prohormone convertase 2 (PCSK2 or PC2) had broad expression in small intestine and appendiceal NETs. Because the study did not include duodenal NETs, we examined PCSK2 expression in duodenal and other GI NETs.

GI NETs (n = 69) and 13 corresponding lymph node metastases from stomach, duodenum, pancreas, ileum, appendix, and rectum were evaluated for the expression of PCSK2, along with ISL1, NKX2.2, CDX2, SATB2, and PAX8. Expression of each stain was evaluated using the H-score system, and differences in expression by site were evaluated by the chi square test.

PCSK2 was expressed at similar frequency in duodenal (50%), pancreatic (59%), and ileal NETs (40%). PCSK2 was infrequently expressed in stomach (0%), appendiceal (8%), and rectal (25%) NETs. However, incorporating PCSK2 into a panel including ISL1, NKX2.2, CDX2, and SATB2 allowed development of an algorithm which had 87% sensitivity and 93% specificity for classification of ileal NETs; and 68% sensitivity and 98% specificity for pancreaticoduodenal NETs.

In contrast to previous findings, PCSK2 does not show specificity for any particular GI site. An algorithmic approach incorporating the expression of PCSK2 with that of ISL1, NKX2.2, CDX2, and SATB2 is useful in discriminating pancreatic, duodenal, ileal, appendiceal, and rectal NETs.

Functional Copy-Number Alterations as Diagnostic and Prognostic Biomarkers in Neuroendocrine Tumors

Functional copy-number alterations (fCNAs) are DNA copy-number changes with concordant differential gene expression. These are less likely to be bystander genetic lesions and could serve as robust and reproducible tumor biomarkers. To identify candidate fCNAs in neuroendocrine tumors (NETs), we integrated chromosomal microarray (CMA) and RNA-seq differential gene-expression data from 31 pancreatic (pNETs) and 33 small-bowel neuroendocrine tumors (sbNETs). Tumors were resected from 47 early-disease-progression (<24 months) and 17 late-disease-progression (>24 months) patients. Candidate fCNAs that accurately differentiated these groups in this discovery cohort were then replicated using fluorescence in situ hybridization (FISH) on formalin-fixed, paraffin-embedded (FFPE) tissues in a larger validation cohort of 60 pNETs and 82 sbNETs (52 early- and 65 late-disease-progression samples). Logistic regression analysis revealed the predictive ability of these biomarkers, as well as the assay-performance metrics of sensitivity, specificity, and area under the curve. Our results indicate that copy-number changes at chromosomal loci 4p16.3, 7q31.2, 9p21.3, 17q12, 18q21.2, and 19q12 may be used as diagnostic and prognostic NET biomarkers. This involves a rapid, cost-effective approach to determine the primary tumor site for patients with metastatic liver NETs and to guide risk-stratified therapeutic decisions.

SATB2 Cytoplasmic Expression is Characteristic of a Subset of Ovarian Stromal Cells and Sex Cord Stromal Tumors

Special AT-rich sequence-binding protein 2 (SATB2) is a nuclear transcription factor that shows consistent nuclear staining in colorectal adenocarcinoma and osteosarcoma. Following the observation of cytoplasmic staining with this marker in luteinized ovarian stromal cells, we studied the expression of SATB2 in ovarian stromal cells, various types of follicular cysts, and sex cord-stromal tumors. Eighty-five cases were stained for SATB2. Ovarian hilar Leydig cells (n = 12), luteinized stromal cells (n = 10), corpora lutea (n = 4), luteinized follicular cysts (n = 4), and stromal hyperthecosis (n = 6) exhibited consistent, usually diffuse, granular cytoplasmic staining. In addition, Leydig cell tumors (n = 1) and steroid cell tumors (n = 4) showed diffuse cytoplasmic staining. SATB2 also exhibited cytoplasmic staining in most Sertoli-Leydig cell tumors (n = 16) and gynandroblastomas (n = 3) confined to the Leydig cell component. Adult granulosa cell tumors (n = 14), juvenile granulosa cell tumors (n = 3), sex cord tumors with annular tubules (n = 3), cellular fibromas (n = 3), sclerosing stromal tumors (n = 1), and thecomas (n = 1) were negative apart from cytoplasmic staining in associated luteinized stromal cells. SATB2 cytoplasmic staining has not been previously described in these lesions but is characteristic of a variety of ovarian stromal cells and sex cord-stromal tumors, in particular, those exhibiting luteinization or a Leydig or steroid cell component. SATB2 staining may be of value in identifying luteinized or Leydig cells when these are morphologically inconspicuous.

Oncogenic Role of SATB2 In Vitro: Regulator of Pluripotency, Self-Renewal, and Epithelial-Mesenchymal Transition in Prostate Cancer

Special AT-rich sequence binding protein-2 (SATB2) is a nuclear matrix protein that binds to nuclear attachment regions and is involved in chromatin remodeling and transcription regulation. In stem cells, it regulates the expression of genes required for maintaining pluripotency and self-renewal and epithelial-mesenchymal transition (EMT). In this study, we examined the oncogenic role of SATB2 in prostate cancer and assessed whether overexpression of SATB2 in human normal prostate epithelial cells (PrECs) induces properties of cancer stem cells (CSCs). The results demonstrate that SATB2 is highly expressed in prostate cancer cell lines and CSCs, but not in PrECs. Overexpression of SATB2 in PrECs induces cellular transformation which was evident by the formation of colonies in soft agar and spheroids in suspension. Overexpression of SATB2 in PrECs also resulted in induction of stem cell markers (CD44 and CD133), pluripotency-maintaining transcription factors (cMYC, OCT4, SOX2, KLF4, and NANOG), CADHERIN switch, and EMT-related transcription factors. Chromatin immunoprecipitation assay demonstrated that SATB2 can directly bind to promoters of BCL-2, BSP, NANOG, MYC, XIAP, KLF4, and HOXA2, suggesting SATB2 is capable of directly regulating pluripotency/self-renewal, cell survival, and proliferation. Since prostate CSCs play a crucial role in cancer initiation, progression, and metastasis, we also examined the effects of SATB2 knockdown on stemness. SATB2 knockdown in prostate CSCs inhibited spheroid formation, cell viability, colony formation, cell motility, migration, and invasion compared to their scrambled control groups. SATB2 knockdown in CSCs also upregulated the expression of E-CADHERIN and inhibited the expression of N-CADHERIN, SNAIL, SLUG, and ZEB1. The expression of SATB2 was significantly higher in prostate adenocarcinoma compared to normal tissues. Overall, our data suggest that SATB2 acts as an oncogenic factor where it is capable of inducing malignant changes in PrECs by inducing CSC characteristics.

The Clinicopathological Significance of Tumor Cell Subtyping in Appendiceal Neuroendocrine Tumors: A Series of 135 Tumors

Appendiceal neuroendocrine tumors (NETs) are common and often are identified as incidental lesions at the time of appendectomy. The guidelines for management are based on tumor size, degree of invasion, and the Ki67 proliferation index. Most small bowel NETs are composed of serotonin-producing EC-cells, but there are multiple other neuroendocrine cell types. In the rectum, there are L-cell tumors that express peptide YY (PYY), glucagon-like peptides (GLPs), and pancreatic polypeptide (PP); they are thought to have a better prognosis than serotonin-producing tumors. We investigated whether the appendix has distinct neuroendocrine tumor types based on cell type and whether that distinction has clinical significance. We collected 135 appendiceal NETs from the pathology archives of UHN Toronto and UHCMC (Cleveland). We analyzed the expression of biomarkers including CDX2, SATB2, PSAP, serotonin, glucagon (that detects GLPs), PYY, and pancreatic polypeptide (PP) and correlated the results with clinicopathologic parameters. Immunohistochemistry identified three types of appendiceal NETs. There were 75 (56%) classified as EC-cell tumors and 37 (27%) classified as L-cell tumors; the remaining 23 (17%) expressed serotonin and one of the L-cell biomarkers and were classified as mixed. EC-cell tumors were significantly larger with more extensive invasion involving the muscularis propria, subserosa, and mesoappendix compared with L-cell tumors. Mixed tumors were intermediate in all of these parameters. Both EC-cell and mixed tumors had lymphatic and/or vascular invasion while L-cell tumors had none. Unlike EC-cell NETs, L-cell tumors were not associated with lymph node metastasis. Tumor type correlated with pT stage and the only patient with distant metastatic disease in this series had an EC-cell tumor. Our study confirms that appendiceal NETs are not a homogeneous tumor population. There are at least three types of appendiceal NET, including EC-cell, L-cell, and mixed tumors. This information is important for surveillance of patients, as monitoring urinary 5HIAA levels is only appropriate for patients with serotonin-producing tumors, whereas measurement of GLPs and/or PP is more appropriate for patients with L-cell tumors. Our data also show that tumor type is of significance with EC-cell tumors exhibiting the most aggressive behavior.

SATB2, CKAE1/AE3, and synaptophysin as a sensitive immunohistochemical panel for the detection of lymph node metastases of Merkel cell carcinoma

Histopathological evaluation of lymph nodes in Merkel cell carcinoma has become crucial in progression estimation and treatment modification. This study was undertaken to determine the most sensitive immunohistochemical panel for detecting MCC nodal metastases. We included 56 patients with 102 metastatic MCC lymph nodes, which were tested with seven antibodies: cytokeratin (CKAE1/AE3), CK20, chromogranin A, synaptophysin, INSM1, SATB2, and neurofilament (NF). Tissue microarrays (TMA) composed of 2-mm tissue cores from each nodal metastasis were constructed. A semiquantitative 5-tier scoring system (0%, < 25%, 25-74%, 75-99%, 100% positive MCC cells with moderate to strong reactivity) was implemented. In the statistical assessment, we included Merkel cell polyomavirus (MCPyV) status and expression heterogeneity between lymph nodes from one patient. A cumulative percentage of moderate to strong expression ≥ 75% of tumoral cells was observed for single cell markers as follows: 91/102 (89.2%) SATB2, 85/102 (83%) CKAE1/AE3, 80/102 (78.4%) synaptophysin, 75/102 (75.5%) INSM1, 68/102 (66.7%) chromogranin A, 60/102 cases (58.8%) CK20, and 0/102 (0%) NF. Three markers presented a complete lack of immunoreactivity: 8/102 (7.8%) CK20, 7/102 (6.9%) chromogranin A, and 6/102 (5.9%) NF. All markers showed expression heterogeneity in lymph nodes from one patient; however, the most homogenous was INSM1. The probability of detecting nodal MCC metastases was the highest while using SATB2 as a first-line marker (89.2%) with subsequential adding CKAE1/AE3 (99%); these results were independent of MCPyV status. Synaptophysin showed a superior significance in confirming the neuroendocrine origin of metastatic cells. This comprehensive analysis allows us to recommend simultaneous evaluation of SATB2, CKAE1/AE3, and synaptophysin in the routine pathologic MCC lymph node protocol.

Clinicopathologic and Molecular Characterization of Anorectal Neuroendocrine Carcinomas Reveals Human Papillomavirus, p53, and c-Myc as Alternative Mechanisms of Carcinogenesis

Poorly differentiated neuroendocrine carcinomas (NECs) are rare malignant neoplasms with aggressive behavior. The diagnosis remains challenging due to ever-changing terminologies and morphologic overlaps with other disease entities. Herein, we seek to better define anorectal NECs by high-risk human papillomavirus (HPV) status and molecular profiling. Fourteen cases, including 3 men and 11 women with a median age of 63 years, were included. High-risk HPV RNA in situ hybridization was diffusely positive (+) in 7 cases, focal rarely positive (+/-) in 2 cases, and completely negative (-) in 5 cases. By morphology, all HPV(-) NECs were large-cell type, 3 mixed with a tubular adenoma/dysplasia or invasive adenocarcinoma. HPV-related (+ or +/-) NECs were mostly small-cell type, 3 mixed with squamous dysplasia and/or squamous cell carcinoma. Immunohistochemically, all NECs were positive for at least 2 neuroendocrine markers. The HPV(-) NECs were also positive for CDX2, whereas all HPV-related NECs were negative or only focally positive for CDX2, p40, and p63. Overexpression of p53 was found in 3 HPV(-) and 2 HPV(+/-) NECs but not in any HPV(+) NECs. Molecular analysis revealed MYC gene amplification in 4 cases: 2 HPV(-), 1 HPV(+/-), and 1 HPV(+). This was confirmed by fluorescence in situ hybridization in all but 1 HPV(-) NEC, which showed polysomy 8 but no true MYC amplification. Interestingly, only 2 of the 4 MYC amplification-bearing cases, both p53 normal/wild-type, expressed c-Myc protein by immunohistochemistry. The other 2 cases, both p53 overexpressed, did not show c-Myc expression despite true MYC amplification. Our study demonstrates that anorectal NECs arise in HPV-dependent or -independent pathways, with heterogeneous expression of other lineage markers and different molecular signatures. Expressions of p53 and c-Myc proteins appear to be mutually exclusive regardless of HPV status, likely mediating alternative mechanisms of NEC carcinogenesis.

Updates in histopathological classification and tissue biomarkers of digestive neuroendocrine neoplasms: What the clinician should know

Histopathological classifications of neuroendocrine neoplasms (NEN) change regularly and the latest WHO classification published in 2022, which concerns all NEN in the body, attempts to standardize classifications in the different locations. Differentiation and proliferation mainly assessed by Ki-67 index are still the cornerstone of those classifications. However, many markers are now used for diagnostic (to check neuroendocrine differentiation, to identify the site of origin of a metastasis, to help separating high-grade neuroendocrine tumors/NET and neuroendocrine carcinoma/NEC), prognostic or theranostic purposes. NENs are often heterogeneous and this can lead to difficulties in classifications, biomarker and prognostic assessment. These different points are discussed successively in this review, insisting especially on the frequent digestive, gastro-entero-pancreatic (GEP) localizations.

Multidisciplinary Approach to the Diagnosis of Occult Primary Neuroendocrine Neoplasm: A Clinical Challenge

Approximately 11% to 14% of subjects with neuroendocrine neoplasms (NENs) have metastatic lesions with unknown primary origin (UPO), with the majority of UPO-NENs found in the small bowel. Herein, we assessed the available literature on UPO-NENs, focusing on clinical presentation and diagnostic techniques to identify the primary site. The identification of the primary tumor is important as it affects the prognosis; however, the clinical presentation can be non-specific in non-functioning forms. In the presence of metastatic disease, the histological sample is fundamental to obtain immunohistochemical markers that might orientate the clinician in the search for the primary tumor through radiology, functional imaging and endoscopic techniques. In summary, multidisciplinary management plays a key role in UPO-NENs, even more than in other NENs. Molecular biology and gene-expression profiling represent areas of great interest which might be developed in the near future for both the diagnosis and the treatment of these neoplasms.

microRNA-660 Enhances Cisplatin Sensitivity via Decreasing SATB2 Expression in Lung Adenocarcinoma

Increasing evidence suggests that microRNAs' (miRNAs) abnormal expression is one of the main factors of chemotherapy resistance in various cancers. However, the role of miRNAs in lung adenocarcinoma (LUAD) resistance to cisplatin is still unclear. In this study, we analyzed a microarray dataset to investigate miRNAs related to cisplatin resistance in LUAD. The expression of miRNAs in LUAD tissues and cell lines was detected using real-time quantitative polymerase chain reaction (RT-qPCR). Special AT-Rich Sequence-Binding Protein 2 (SATB2) in LUAD cell lines was detected using RT-qPCR and Western blot. Cell proliferation was measured by CCK8 and colony formation assays, while cell cycle and apoptosis were measured by flow cytometry. A dual-luciferase reporter assay was performed to confirm that SATB2 is a target gene of microRNA-660 (miR-660). We showed that the expression of miR-660 was not only decreased in LUAD cells and tissues but also further decreased in the cisplatin-resistant A549 cell line. The overexpression of miR-660 increased cisplatin sensitivity in LUAD cells. In addition, we identified SATB2 as a direct target gene of miR-660. We also revealed that miR-660 increased cisplatin sensitivity in LUAD cells via targeting SATB2. In conclusion, miR-660/SATB2 axis is a key regulator of cisplatin resistance in LUAD.

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.

Expression of SATB2, RUNX2, and SOX9 and possible osteoblastic and chondroblastic differentiation in chondroblastoma

Chondroblastoma (CB) is histologically characterized by oval to polygonal-shaped mononuclear neoplastic cells, multinucleated osteoclastic giant cells, and eosinophilic matrix with occasional calcification. Genetically, the majority of CBs harbor H3F3B p.K36M mutation. Despite the historical nomenclature, it has been reported that the matrix of CB is similar to osteoid rather than true cartilage; however, it remains unclear whether neoplastic cells in CB have the potential for osteoblastic differentiation. To clarify this issue, we immunohistochemically examined the expression of osteogenic and chondrogenic markers (SATB2, RUNX2, p63, and SOX9) as well as H3K36M mutant protein in 33 cases of CB. All 33 cases of CB were positive for H3K36M, while SATB2, RUNX2, p63, and SOX9 were expressed in 30/33 (91%), 33/33 (100%), 29/33 (88%), and 31/32 (97%) CB cases, respectively. Our immunohistochemical results suggest that neoplastic cells in CB frequently express both osteogenic and chondrogenic markers and may have an intermediate feature of osteoblastic and chondroblastic nature.

Diagnostic accuracy of SATB2 in identifying primary and metastatic colorectal carcinoma: a comparative immunohistochemical study

Special AT-rich sequence-binding protein 2 (SATB2) is a new marker that could identify the colonic origin, but whether its expression is preserved in metastatic colorectal carcinomas (CRCs) remains unclear. This study was designed to investigate SATB2 validity in the identification of CRC either alone or in combination with caudal-type homeobox 2 (CDX2) and/or cytokeratin 20 (CK20). Moreover, we examined the concordance of SATB2 expression in primary CRC and paired metastatic specimen. Immunohistochemical expression of SATB2, CDX2 and CK20 was evaluated in primary CRC, 50 paired metastatic CRC and 80 non-CRC specimens. This study demonstrated that the ideal SATB2 cut-off value for recognising colonic from non-colonic origin was 10%. SATB2 was more sensitive and specific than CK20. However, it was more specific but less sensitive than CDX2. Analysing the combined markers expression, SATB2 and CDX2 combination revealed better sensitivity, specificity and larger area under curve compared to SATB2 alone, CDX2 alone and combined CDX2 and CK20. Moreover, SATB2 was able to retain its expression at the metastatic sites. SATB2 was totally concordant between primary CRC and their paired metastatic sites (concordance rate = 100%) with perfect level of agreement. SATB2 could be considered as an accurate diagnostic marker of primary and metastatic CRC. SATB2 and CDX2 is the best combination serving the highest sensitivity and specificity in detection of CRC.

Nationwide multidisciplinary consensus on the clinical management of Merkel cell carcinoma: a Delphi panel

Merkel cell carcinoma (MCC) is a rare and highly aggressive cutaneous neuroendocrine carcinoma. The MCC incidence rate has rapidly grown over the last years, with Italy showing the highest increase among European countries. This malignancy has been the focus of active scientific research over the last years, focusing mainly on pathogenesis, new therapeutic trials and diagnosis. A national expert board developed 28 consensus statements that delineated the evolution of disease management and highlighted the paradigm shift towards the use of immunological strategies, which were then presented to a national MCC specialists panel for review. Sixty-five panelists answered both rounds of the questionnaire. The statements were divided into five areas: a high level of agreement was reached in the area of guidelines and multidisciplinary management, even if in real life the multidisciplinary team was not always represented by all the specialists. In the diagnostic pathway area, imaging played a crucial role in diagnosis and initial staging, planning for surgery or radiation therapy, assessment of treatment response and surveillance of recurrence and metastases. Concerning diagnosis, the usefulness of Merkel cell polyomavirus is recognized, but the agreement and consensus regarding the need for cytokeratin evaluation appears greater. Regarding the areas of clinical management and follow-up, patients with MCC require customized treatment. There was a wide dispersion of results and the suggestion to increase awareness about the adjuvant radiation therapy. The panelists unanimously agreed that the information concerning avelumab provided by the JAVELIN Merkel 200 study is adequate and reliable and that the expanded access program data could have concrete clinical implications. An immunocompromised patient with advanced MCC can be treated with immunotherapy after multidisciplinary risk/benefit assessment, as evidenced by real-world analysis and highlighted in the guidelines. A very high consensus regarding the addition of radiotherapy to treat the ongoing focal progression of immunotherapy was observed. This paper emphasizes the importance of collaboration and communication among the interprofessional team members and encourages managing patients with MCC within dedicated multidisciplinary teams. New insights in the treatment of this challenging cancer needs the contribution of many and different experts.

Transcription Factor Expression in Sinonasal Neuroendocrine Neoplasms and Olfactory Neuroblastoma (ONB): Hyams' Grades 1-3 ONBs Expand the Spectrum of SATB2 and GATA3-Positive Neoplasms

Sinonasal neuroendocrine neoplasms (SN-NENs) are rare and mostly include neuroendocrine carcinoma (NEC), whereas neuroendocrine tumor (NET) is exceptional in this site. Olfactory neuroblastoma (ONB) is a malignant neuroectodermal neoplasm arising in the nasal cavity. Albeit crucial for correct patients' management, the distinction of high grade ONB from NEC is challenging and requires additional diagnostic markers. The transcription factor SATB2 has been recently introduced in routine diagnostics as an immunohistochemical marker of distal intestine differentiation. No specific data are available about SATB2 and GATA3 expression in SN-NENs. GATA3, SATB2, and, for comparison, CDX2 expression were investigated in a series of epithelial and non-epithelial SN-NENs. We collected 26 cases of ONB and 7 cases of epithelial SN-NENs diagnosed and treated in our Institution. ONBs were graded according to Hyams' system and epithelial NENs were reclassified into 5 NECs, 1 MiNEN, and 1 amphicrine carcinoma. Immunohistochemistry was performed using standard automated protocols. Hyams' grades 1-3 ONBs stained diffusely and intensely for SATB2, whereas grade 4 ONBs and NECs were globally negative. The non-neuroendocrine component of MiNEN and the amphicrine carcinoma were strongly positive. GATA3 was heterogeneously and unpredictably expressed in Hyams' grades 1-3 ONBs, whereas grade 4 ONBs and NECs were completely negative. CDX2 was negative in all cases. Our study identifies, for the first time, SATB2 and GATA3 expression as features of Hyams' grades 1-3 ONBs, expands the spectrum of SATB2 and GATA3-positive neoplasms, and suggests that Hyams' grade 4 ONBs are not only clinically but also biologically different from low graded ONBs.

Diagnosis in Neuroendocrine Neoplasms: From Molecular Biology to Molecular Imaging

Simple Summary

Neuroendocrine neoplasms are a small group of malignancies with a diverse prognosis and behaviour. In order to offer an adequate treatment, physicians need to perform a proper diagnosis, staging and stratification. This review aims to help to integrate the information from pathology, immunohistochemistry, molecular biology and imaging to guide this process.

Abstract

Neuroendocrine neoplasms (NENs) are a heterogeneous group of tumours with a diverse behaviour, biology and prognosis, whose incidence is gradually increasing. Their diagnosis is challenging and a multidisciplinary approach is often required. The combination of pathology, molecular biomarkers, and the use of novel imaging techniques leads to an accurate diagnosis and a better treatment approach. To determine the functionality of the tumour, somatostatin receptor expression, differentiation, and primary tumour origin are the main determining tumour-dependent factors to guide treatment, both in local and metastatic stages. Until recently, little was known about the biological behaviour of these tumours. However, in recent years, many advances have been achieved in the molecular characterization and diagnosis of NENs. The incorporation of novel radiotracer-based imaging techniques, such as ⁶⁸Gallium-DOTATATE PET-CT, has significantly increased diagnostic sensitivity, while introducing the theragnosis concept, offering new treatment strategies. Here, we will review current knowledge and novelties in the diagnosis of NENs, including molecular biology, pathology, and new radiotracers.

New insights in diagnosis and treatment of gastroenteropancreatic neuroendocrine neoplasms

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are rare epithelial neoplasms derived from pluripotent endocrine cells along the gastrointestinal tract and pancreas. GEP-NENs are classified into well-differentiated neuroendocrine tumors and poorly differentiated neuroendocrine carcinomas. Despite overlapping morphological features, GEP-NENs vary in molecular biology, epigenetic, clinical behavior, treatment response, and prognosis features and remain an unmet clinical challenge. In this review, we introduce recent updates on the histopathologic classification, including the tumor grading and staging system, molecular genetics, and systemic evaluation of the diagnosis and treatment of GEP-NENs at different anatomic sites, together with some insights into the diagnosis of challenging and unusual cases. We also discuss the application of novel therapeutic approaches for GEP-NENs, including peptide receptor radionuclide therapy, targeted therapy, and immunotherapy with immune checkpoint inhibitors. These findings will help improve patient care with precise diagnosis and individualized treatment of patients with GEP-NENs.

Metastatic Neuroendocrine Neoplasms of Unknown Primary: Clues from Pathology Workup

Simple Summary

While most neuroendocrine neoplasms are indolent and slow-growing tumors, subsets of cases will spread beyond the tissue of origin. Given the rather slow progress, some lesions are incidentally discovered as metastatic deposits rather than primary masses. In these cases, a biopsy is often taken to allow the pathologist to identify the tumor type and possibly the primary tumor site via microscopic examination. In this review, the authors present a simplified guide on how to approach metastatic neuroendocrine tumors from a pathologist’s perspective.

Abstract

Neuroendocrine neoplasms (NENs) are diverse tumors arising in various anatomical locations and may therefore cause a variety of symptoms leading to their discovery. However, there are instances in which a NEN first presents clinically as a metastatic deposit, while the associated primary tumor is not easily identified using conventional imaging techniques because of small primary tumor sizes. In this setting (which is referred to as a “NEN of unknown primary”; NEN-UP), a tissue biopsy is often procured to allow the surgical pathologist to diagnose the metastatic lesion. If indeed a metastatic NEN-UP is found, several clues can be obtained from morphological assessment and immunohistochemical staining patterns that individually or in concert may help identify the primary tumor site. Herein, histological and auxiliary analyses of value in this context are discussed in order to aid the pathologist when encountering these lesions in clinical practice.

SATB2 Expression in Undifferentiated Pleomorphic Sarcomas of Bone

OBJECTIVES

SATB2 is a transcriptional regulator that plays an important role in osteoblastic differentiation. We examined the prevalence and potential significance of SATB2 expression in undifferentiated pleomorphic sarcoma (UPS) of bone.

METHODS

We examined 38 cases of bone UPS without osteoid. The male-to-female ratio was 1:1.4, with a median age of 48 years (range, 23-83 years). Tumors occurred primarily in the femur (n = 8) and ilium (n = 8), with a median tumor size of 9.5 cm (range, 1.8-27.0 cm). The median follow-up was 24.7 months (range, 2-82 months): 11 patients developed local recurrences, and 18 patients had metastases, mainly to lung and bone.

RESULTS

SATB2 expression (nuclear labeling ≥5%) was seen in 21 of 38 (55%) cases: 5 with focal (nuclear labeling 5%), 11 with patchy (nuclear labeling 5%-50%), and 5 with diffuse (nuclear labeling ≥50%) staining. Among this group, diffuse SATB2 expression demonstrated superior metastasis-free survival (P = .036) and event-free survival (P = .024). For comparison, 100 soft tissue UPS were stained; the majority were negative (75/100 [75%]).

CONCLUSIONS

UPS of bone demonstrated more frequent SATB2 expression compared with its soft tissue counterpart. In this series, diffuse SATB2 expression in UPS of bone was associated with better outcomes. Additional studies are still needed to determine its significance.

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.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Overview of the 2022 WHO Classification of Head and Neck Neuroendocrine Neoplasms

This review article provides a brief overview of the new WHO classification by adopting a question-answer model to highlight the spectrum of head and neck neuroendocrine neoplasms which includes epithelial neuroendocrine neoplasms (neuroendocrine tumors and neuroendocrine carcinomas) arising from upper aerodigestive tract and salivary glands, and special neuroendocrine neoplasms including middle ear neuroendocrine tumors (MeNET), ectopic or invasive pituitary neuroendocrine tumors (PitNET; formerly known as pituitary adenoma) and Merkel cell carcinoma as well as non-epithelial neuroendocrine neoplasms (paragangliomas). The new WHO classification follows the IARC/WHO nomenclature framework and restricts the diagnostic term of neuroendocrine carcinoma to poorly differentiated epithelial neuroendocrine neoplasms. In this classification, well-differentiated epithelial neuroendocrine neoplasms are termed as neuroendocrine tumors (NET), and are graded as G1 NET (no necrosis and < 2 mitoses per 2 mm²; Ki67 < 20%), G2 NET (necrosis or 2-10 mitoses per 2 mm², and Ki67 < 20%) and G3 NET (> 10 mitoses per 2 mm² or Ki67 > 20%, and absence of poorly differentiated cytomorphology). Neuroendocrine carcinomas (> 10 mitoses per 2 mm², Ki67 > 20%, and often associated with a Ki67 > 55%) are further subtyped based on cytomorphological characteristics as small cell and large cell neuroendocrine carcinomas. Unlike neuroendocrine carcinomas, head and neck NETs typically show no aberrant p53 expression or loss of RB reactivity. Ectopic or invasive PitNETs are subtyped using pituitary transcription factors (PIT1, TPIT, SF1, GATA3, ER-alpha), hormones and keratins (e.g., CAM5.2). The new classification emphasizes a strict correlation of morphology and immunohistochemical findings in the accurate diagnosis of neuroendocrine neoplasms. A particular emphasis on the role of biomarkers in the confirmation of the neuroendocrine nature of a neoplasm and in the distinction of various neuroendocrine neoplasms is provided by reviewing ancillary tools that are available to pathologists in the diagnostic workup of head and neck neuroendocrine neoplasms. Furthermore, the role of molecular immunohistochemistry in the diagnostic workup of head and neck paragangliomas is discussed. The unmet needs in the field of head and neck neuroendocrine neoplasms are also discussed in this article. The new WHO classification is an important step forward to ensure accurate diagnosis that will also form the basis of ongoing research in this field.

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.

SATB2 is expressed in neuroendocrine carcinoma of the uterine cervix

Neuroendocrine carcinoma (NEC) of the uterine cervix is less characterized than neuroendocrine neoplasms of other sites such as of the digestive system and the lung. Special AT-rich sequence-binding protein 2 (SATB2) recently emerged as a marker of well-differentiated neuroendocrine tumors of the lower gastrointestinal (GI) tract. Among NECs, SATB2 is more frequently expressed in cutaneous Merkel cell carcinoma than in NEC of other anatomical sites. In our study, we performed an immunohistochemical study of SATB2 in 16 NECs of the uterine cervix, where the expression of these markers is still undefined. SATB2 was expressed in 12/16 cervical NECs (75%), with 7/16 cases (44%) showing SATB2 positivity in ≥ 50% of cells. In 7 cervical NECs associated with a non-neuroendocrine component, the expression of SATB2 was restricted to the neuroendocrine component. SATB2 was positive in all cases that expressed CDX2 (n = 7) and TTF1 (n = 5), with no evident association with p16 and p53. Our study demonstrated that SATB2 is often expressed in NECs of the uterine cervix. This information should be taken into account when assessing the origin of a NEC.

Merkel cell carcinoma presenting as a malignant pleural effusion post-COVID-19 hospitalization: A case report and literature review

Merkel cell carcinoma (MCC) is a rare, highly aggressive neuroendocrine carcinoma of the skin, associated with immunosuppression, UV light exposure, and the Merkel cell polyomavirus (MCPyV). Cases of metastatic MCC diagnosed in body fluid cytology are extremely rare; only five cases have been reported previously in the English literature. We present a case of a 65-year-old male with acute respiratory failure and an enlarged right pleural effusion. He had two hospitalizations for COVID-19 pneumonia 2 months prior, for which he received steroid treatment and tocilizumab. Emergent thoracentesis was done, with pleural fluid sent for cytologic evaluation. Both the Papanicolaou stained ThinPrep slide and cell block demonstrated clusters of predominantly small to medium sized blue round cells with hyperchromatic nuclei, scant cytoplasm and fine chromatin, in a background of rare mesothelial cells, macrophages and numerous lymphocytes. Tumor cells were positive for CD56, chromogranin, synaptophysin, SAT2B, MCPyV, and CK20 in perinuclear dot like pattern, while negative for TTF-1 and CD45 immunostains. Ki67 proliferative index was approximately 40%. The patient had a history of MCC of the right ulnar forearm 4 years before the current presentation, which was unknown to us at the time of cytologic evaluation. To the best of our knowledge, this is the sixth case of metastatic MCC diagnosed by fluid cytology and the first reported in a patient receiving immunosuppressive treatment for COVID-19. Further reporting of such cases may increase awareness, especially when prior history is not readily available, such as in our case.

Expression of nSATB2 in Neuroendocrine Carcinomas of the Lung: Frequent Immunopositivity of Large Cell Neuroendocrine Carcinoma with a Diagnostic Pitfall

Small cell lung carcinoma (SCLC) and pulmonary large cell neuroendocrine carcinoma (LCNEC) are both classified as lung neuroendocrine carcinoma (NEC). It has recently been reported that the special AT-rich sequence-binding protein 2 (STAB2), known as a colorectal cancer marker, is also expressed in NECs occurring in various organs including the lung. However, few studies have examined any differences of SATB2 immunopositivity between SCLC and LCNEC. We investigated SATB2 expression in 45 SCLC and 14 LCNEC cases using immunohistochemistry as well as the expression of caudal-type homeobox 2 (CDX2) and keratin (KRT) 20. The LCNEC cases were more frequently positive for SATB2 (ten out of 14, 71%) than the SCLC ones (seventeen out of 45, 38%) with a statistically significance (P = 0.035). Furthermore, two LCNEC cases were positive for CDX2 while no positive findings were observed for any SCLC cases, the difference of which, however, was not statistically significant (P = 0.053). KRT20 was negative in all LCNEC and SCLC cases. These results require our attention when we use SATB2 and CDX2 as colorectal cancer markers because their expression in pulmonary NECs can lead to a misdiagnosis that the tumor is of metastatic colorectal adenocarcinoma, especially when the patient has a past history of colorectal cancer. Analyzing the relationship between the demographic/clinical variables and the SATB2 expression in the SCLC cases, just high Brinkman index (≥ 600) was significantly related to the positivity of SATB2 (P = 0.017), which is interesting considering the strong relationship between SCLC and smoking.

Middle Ear "Adenoma": a Neuroendocrine Tumor with Predominant L Cell Differentiation

This morphological and immunohistochemical study demonstrates that tumors currently known as "middle ear adenomas" are truly well-differentiated epithelial neuroendocrine tumors (NETs) composed of cells comparable to normal intestinal L cells, and therefore, these tumors resemble hindgut NETs. These tumors show consistent expression of glucagon, pancreatic polypeptide, PYY, and the transcription factor SATB2, as well as generic neuroendocrine markers and keratins. The same L cell markers are expressed by cells within the normal middle ear epithelium. These markers define a valuable immunohistochemical profile that can be used for differential diagnosis of middle ear neoplasms, particularly in distinguishing epithelial NETs from paragangliomas. The discovery of neuroendocrine cells expressing the same markers in non-neoplastic middle ear mucosa opens new areas of investigation into the physiology of the normal middle ear and the pathophysiology of middle ear disorders.

CDX2 and SATB2 positivity in pilomatrix carcinoma: Avoiding an erroneous diagnosis of cutaneous metastasis of gastrointestinal origin

An 80-year-old female presented with a slowly growing 2-cm nodule on her shoulder over a 1-year period. Histopathologic sections of a biopsy specimen showed a multinodular, dermal-based basaloid tumor with areas of clear-cell change, stromal induction, as well as significant cytologic atypia and atypical mitotic activity. An initial investigation revealed positive staining of CDX2, a well-known marker of tumors of gastrointestinal origin. The case was referred to our dermatopathology service for consultation to determine if the lesion was in keeping with a cutaneous metastasis. On receipt of the case, an extended immunohistochemical panel was performed including SATB2, which displayed a similar pattern of staining as seen with CDX2. Although pathologists are most familiar with CDX2 and SATB2 as markers of gastrointestinal origin, the recent dermatopathology literature highlights that primary adnexal lesions of the skin also display positivity for CDX2 and can exhibit SATB2 positivity. We share a case of pilomatrix carcinoma with positive expression of nuclear CDX2 and SATB2, adding to the recent literature to (a) increase recognition of this staining pattern in hair follicle tumors, and (b) discuss briefly the shared molecular underpinnings in the tumorigenesis of gastrointestinal tumors and tumors of hair follicle origin that help clarify this underrecognized immunohistochemical pattern.

SATB2 Is Expressed in a Subset of Pulmonary and Thymic Neuroendocrine Tumors

OBJECTIVES

To evaluate SATB2 expression and prognostic implications in a large cohort of thoracic neuroendocrine tumors.

METHODS

Surgical pathology files (1995-2017) and an institutional thymic epithelial tumor database (2010-2020) were searched for resected neuroendocrine tumors. Cases were stained with SATB2 (clone EP281). Percent SATB2-positive tumor cells and expression intensity were scored.

RESULTS

In the lung, SATB2 was expressed in 5% or more of tumor cells in 29 (74.4%) of 39 small cell carcinomas and 9 (22.5%) of 40 atypical and 26 (40.6%) of 64 typical carcinoid tumors. SATB2 percent tumor cell expression and intensity were higher in small cell carcinomas than in carcinoid tumors (both P < .001, respectively). After adjusting for tumor subtype, SATB2 expression did not correlate with outcome. In the thymus, four (100%) of four atypical carcinoid tumors and one large cell neuroendocrine carcinoma but no small cell carcinoma (n = 2) expressed SATB2 in 5% or more of tumor cells.

CONCLUSIONS

SATB2 (clone EP281) is expressed in a large subset of pulmonary and thymic neuroendocrine tumors and therefore does not appear to be a useful marker to identify the origin of neuroendocrine tumors. Validation studies are needed, specifically including thymic neuroendocrine tumors, as the expression pattern might be different in those tumors.

Poorly differentiated neuroendocrine carcinomas of the gastrointestinal tract: A single-institute study of 43 cases

OBJECTIVES

To characterize the clinicopathologic and immunohistochemical features of poorly differentiated neuroendocrine carcinomas (NEC) in the gastrointestinal tract.

DESIGN

A total of 43 cases were identified and reassessed based on modern classification.

RESULTS

The cohort (27M, 16F; median age: 66 years) included 16 (37%) large cell NEC, 12 (28%) small cell NEC, 5 (12%) NEC not otherwise specified, and 10 (23%) mixed adenoneuroendocrine carcinomas. Tumor predominantly involved the colon (n = 14, 33%), rectum (n = 13, 30%), and esophagus (n = 9, 21%). Immunohistochemically, INSM1 was the most sensitive marker for neuroendocrine differentiation (28/28, 100%), followed by synaptophysin (40/43, 93%), CD56 (22/35, 63%), and chromogranin (18/40, 45%). SATB2, CDX2, CK20, CK7, abnormal p53, and PD-L1 was positive in 21/26 (81%), 26/37 (70%), 11/35 (31%), 10/35 (29%), 19/24 (79%), and 12/23 (52%) cases, respectively. Three of 25 (11%) were mismatch repair protein deficient. Of 21 resected tumors, 19 (90%) were ≥ pT3 and 13 (62%) had nodal metastasis. Twenty-eight (65%) had distant metastasis. The 5-year survival rate was 21%. The prognosis was stage dependent (p < 0.05), but not associated with tumor type, location, or specific immunomarkers.

CONCLUSION

Gastrointestinal NECs are aggressive neoplasms. INSM1, synaptophysin, and SATB2 are sensitive markers, although not site or tumor type specific.

Doxycycline alleviates acute traumatic brain injury by suppressing neuroinflammation and apoptosis in a mouse model

Traumatic brain injury (TBI) is one of the significant causes of death among young people worldwide. Doxycycline (DOX), an antibiotic with anti-inflammatory effects, has not been used as a therapeutic agent to modify the inflammatory response after the traumatic brain injury. In this study, intraperitoneal administration of DOX reduced significantly the acute inflammatory markers like IL-6 and CD3, microglial migration to the damaged area marked with Iba-1, and neuronal apoptosis assessed with TUNEL assay at 72 h after the trauma. The low dose, 10 mg/kg of DOX had a dominant anti-inflammatory effect; while the high dose, 100 mg/kg of DOX, was more effective in decreasing neuronal apoptosis. In early hours after the head trauma, use of a low dose (10 mg/kg) of DOX for decreasing the acute form of inflammation followed by a high dose (100 mg/kg) for the anti-apoptotic effects particularly in severe head traumas, would be a promising approach to alleviate the brain injury.

An algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A can help differentiate between gastrointestinal and pulmonary neuroendocrine carcinomas

Primary gastrointestinal neuroendocrine carcinoma (GI-NEC) cannot be distinguished morphologically from pulmonary neuroendocrine carcinoma (P-NEC). This can present a significant diagnostic challenge in cases where site of origin cannot be readily determined. To identify immunohistochemical (IHC) markers that can be used to reliably distinguish between GI-NECs and P-NECs, we constructed 3-mm tissue microarrays, one containing 13 GI-NECs and one containing 20 P-NECs. IHC was performed on both microarrays using 21 stains: AE1/AE3, CK7, CK20, synaptophysin, chromogranin, CD56, INSM1, SSTR2A, CDX2, SATB2, TTF1, Napsin A, PR, GATA3, PAX8, ISL1, beta-catenin, AFP, SMAD4, Rb, and p53. For GI-NEC, the most strongly expressed marker was synaptophysin (mean H-score 248), while AE1/AE3 was the most strongly expressed in P-NEC (mean H-score 230), which was stronger than in GI-NEC (p = 0.011). Other markers that were stronger overall in P-NEC than in GI-NEC included CK7 (p < 0.0001) and TTF1 (p < 0.0001). Markers that were stronger overall in GI-NEC than in P-NEC included SSTR2A (p = 0.0021), SATB2 (p = 0.018), CDX2 (p = 0.019), and beta-catenin (nuclear; p = 0.029). SMAD4, Rb, and p53 showed similar rates of abnormal protein expression. Based on these results, a stepwise algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A had a 91% overall accuracy in distinguishing these GI-NEC from P-NEC. This was tested on a second cohort of 10 metastatic GI-NEC and 10 metastatic P-NEC, with an accuracy in this cohort of 85% and an overall accuracy of 89% for the 53 cases tested. Our algorithm reasonably discriminates GI-NEC from P-NEC using currently available IHC stains.

Small Bowel Adenocarcinomas Featuring Special AT-Rich Sequence-Binding Protein 2 (SATB2) Expression and a Colorectal Cancer-Like Immunophenotype: A Potential Diagnostic Pitfall

Simple Summary

Since small bowel adenocarcinoma may mimic a colorectal primary neoplasm histologically, it is pivotal to find biomarkers to discriminate these two biologically distinct neoplasms. The aim of our study was to evaluate the expression of special AT-rich sequence-binding protein 2 (SATB2), expressed in the vast majority of colorectal carcinomas, and other gastrointestinal phenotypic markers, such as cytokeratin 7, cytokeratin 20 and caudal type homeobox 2 (CDX2), in 100 small bowel adenocarcinomas. We identified 20 SATB2-positive small bowel adenocarcinomas, including nine sporadic cancers, seven celiac disease-associated cancers and four Crohn’s disease-associated small bowel adenocarcinomas. Six small bowel adenocarcinomas, including two cases associated with celiac disease and four sporadic, displayed a full colorectal carcinoma-like immunoprofile. Unlike SATB2, cytokeratin patterns stratified small bowel adenocarcinoma patient prognosis. The small bowel should be considered as one of the possible sites of origin in cancers of unknown primary, even when the neoplasm shows a colorectal carcinoma-like immunoprofile.

Abstract

Special AT-rich sequence-binding protein 2 (SATB2) is a transcription factor expressed by colonic cryptic epithelium and epithelial neoplasms of the lower gastrointestinal (GI) tract, as well as by small bowel adenocarcinomas (SBAs), though at a lower rate. Nevertheless, up to now, only small SBA series, often including a very limited number of Crohn’s disease-associated SBAs (CrD-SBAs) and celiac disease-associated SBAs (CD-SBA), have been investigated for SATB2 expression. We evaluated the expression of SATB2 and other GI phenotypic markers (cytokeratin (CK) 7 and CK20, caudal type homeobox 2 (CDX2) and alpha-methylacyl-CoA racemase (AMACR)), as well as mismatch repair (MMR) proteins, in 100 SBAs, encompassing 34 CrD-SBAs, 28 CD-SBAs and 38 sporadic cases (Spo-SBAs). Any mutual association and correlation with other clinico-pathologic features, including patient prognosis, were searched. Twenty (20%) SATB2-positive SBAs (4 CrD-SBAs, 7 CD-SBAs and 9 Spo-SBAs) were identified. The prevalence of SATB2 positivity was lower in CrD-SBA (12%) in comparison with both CD-SBAs (25%) and Spo-SBAs (24%). Interestingly, six SBAs (two CD-SBAs and four Spo-SBAs) displayed a full colorectal carcinoma (CRC)-like immunoprofile (CK7−/CK20+/CDX2+/AMACR+/SATB2+); none of them was a CrD-SBA. No association between SATB2 expression and MMR status was observed. Although SATB2-positive SBA patients showed a more favorable outcome in comparison with SATB2-negative ones, the difference did not reach statistical significance. When cancers were stratified according to CK7/CK20 expression patterns, we found that CK7−/CK20- SBAs were enriched with MMR-deficient cases (71%) and patients with CK7−/CK20− or CK7−/CK20+ SBAs had a significantly better survival rate compared to those with CK7+/CK20− or CK7+/CK20+ cancers (p = 0.002). To conclude, we identified a small (6%) subset of SBAs featuring a full CRC-like immunoprofile, representing a potential diagnostic pitfall in attempts to identify the site of origin of neoplasms of unknown primary site. In contrast with data on colorectal carcinoma, SATB2 expression is not associated with MMR status in SBAs. CK patterns influence patient survival, as CK7−/CK20− cancers show better prognosis, a behavior possibly due to the high rate of MMR-deficient SBAs within this subgroup.

YJ5 as an immunohistochemical marker of osteogenic lineage

Overexpression of WLS, an upstream protein in the Wnt pathway, has been implicated in several non-osteogenic tumours. This study represents the first attempt at evaluating WLS expression in various bone and soft tissue tumours using YJ5, a monoclonal antibody specific to WLS, with the aim of elucidating its utility in discerning tumours with aberrant Wnt signalling and as a marker of osteogenic lineage in challenging cases. Tumour tissue sections of 144 bone mass lesions and 63 soft tissue mass lesions were immunostained with the YJ5 antibody following standardised protocols. Subsequent assessment of immunoreactivity segregated cases into one of three groups: absent/weak, moderate, or strong YJ5 immunoreactivity. For the bone tumours, strong YJ5 immunoreactivity was seen in almost all osteosarcomas and chondroblastomas, all osteoblastomas and osteoid osteomas. In contrast, all other cartilaginous tumours, chordomas, aneurysmal bone cysts, chondromyxoid fibromas, most fibrous dysplasias and most giant cell tumours exhibited absent/weak YJ5 immunostaining. For the soft tissue tumours, a more heterogeneous pattern of YJ5 immunoreactivity was observed. Because diffuse and strong YJ5 expression is identified in almost all benign and malignant bone tumours with osteoblastic activity, it can be potentially utilised as an immunohistochemical marker to support osteogenic lineage. If interpreted in the appropriate context, this marker is useful in determining whether a malignant bone tumour is an osteosarcoma, particularly in those subtypes with no or minimal osteoid or unusual morphological features. This marker can also complement SATB2 to denote osteogenic lineage.

SATB2 is a novel biomarker and therapeutic target for cancer

Several studies have confirmed the involvement of cancer stem cells (CSC) in tumour progression, metastasis, drug resistance and cancer relapse. SATB2 (special AT-rich binding protein-2) acts as a transcriptional co-factor and modulates chromatin architecture to regulate gene expression. The purpose of this review was to discuss the pathophysiological roles of SATB2 and assess whether it could be used as a therapeutic target for cancer. SATB2 modulated the expression of those genes which regulated pluripotency and self-renewal. Overexpression of SATB2 gene in normal epithelial cells was shown to induce transformation, as a result transformed cells gained CSC's characteristics by expressing stem cell markers and pluripotency maintaining factors, suggesting its role as an oncogene. In addition, SATB2 induced epithelial-mesenchymal transition (EMT) and metastasis. Interestingly, the expression of SATB2 was positively correlated with the activation of β-catenin/TCF-LEF pathway. Furthermore, SATB2 silencing inhibited EMT and their positive regulators, and tumour growth, and suppressed the expression of stem cell markers, pluripotency maintaining factors, cell cycle and cell survival genes, and TCF/LEF targets. Based on the cancer genome atlas (TCGA) expression data and published papers, SATB2 alone or in combination with other proteins could be used a diagnostic biomarker for cancer. Although there is no pharmacological inhibitor of SATB2, studies using genetic approaches suggest that SATB2 could be a potential target for cancer treatment and prevention.

Hepatocellular carcinomas can be Special AT-rich sequence-binding protein 2 positive: an important diagnostic pitfall

Special AT-rich sequence-binding protein 2 (SATB2) is a sensitive and specific marker for tumors originating with the colon and appendix. It is now commonly used in surgical pathology, while working up carcinomas of unknown primary. We had anecdotally encountered occasional hepatocellular carcinomas (HCCs) that were SATB2 positive. Immunohistochemical expression of SATB2 in HCC has not yet been examined in detail. In this study, we evaluated SATB2 expression in 46 HCCs. Nineteen (41%) of 46 HCCs were positive for SATB2. SATB2 expression in HCCs was more commonly seen in poorly differentiated tumors (11 of 13 cases, 85%) than well and moderately differentiated tumors (8 of 33 cases, 24%), p value = 0.0001. No other statistically significant correlations were observed (p > 0.05). There were no other statistically significant correlations between SATB2 expression and age, gender, background liver disease, and cirrhosis (p > 0.05). Results of our study show that a significant subset (41%) of HCCs can be SATB2 positive. Awareness of this phenomenon is important as SATB2 expression in a liver tumor does not completely exclude a diagnosis of HCC.

Positivity for SATB2 distinguishes Islet1 positive rectal neuroendocrine tumours from pancreaticoduodenal neuroendocrine tumours

AIMS

Determining the site of origin of a metastatic neuroendocrine tumour (NET) can be challenging and has important prognostic and therapeutic implications. An immunohistochemical (IHC) panel consisting of TTF1, CDX2, PAX8/PAX6 and Islet1 is often employed. However, there can be a significant IHC overlap among different primary sites. Herein, we sought to determine the utility of including Special AT-rich sequence binding protein-2 (SATB2) in the IHC panel that is used for determining the site of origin of a metastatic NET.

METHODS

Paraffin tissue microarrays consisting of 137 primary NETs (26 lung, 22 jejunoileal, 8 appendix, 5 stomach, 4 duodenum, 17 rectum and 55 pancreas) were stained for SATB2, in addition to the well-described lineage-associated markers, such as TTF1, CDX2, PAX6 and Islet1. Additionally, a tissue microarray consisting of 21 metastatic NETs (1 lung, 1 stomach, 8 jejunoileal and 11 pancreas) was stained for TTF1, CDX2, SATB2 and Islet1. The results were recorded as no staining, weak staining and moderate to strong staining.

RESULTS

All appendiceal NETs and majority (88%) of the rectal NETs were positive for SATB2. All primary foregut NETs (stomach, pancreas, duodenum and lung) were negative for SATB2, except for one pulmonary NET with weak staining. However, among the metastatic tumours, 5 of 11 pancreatic NETs, 1 stomach NET, 1 lung NET and 2 of 8 jejunoileal NETs showed weak staining. Receiver operating characteristic analysis incorporating sensitivity and specificity data of IHC panel, considering moderate to strong staining as truly positive cases, showed that inclusion of SATB2 to the previously described NET IHC panel outperformed the panel without SATB2, raising the specificity for pancreaticoduodenal NETs from 81.2% to 100%, with a positive predictive value (PPV) of 100% and negative predictive value (NPV) of 82.22% (p<0.0001); for appendiceal NETs the specificity changed from 99.1% to 98.5% and sensitivity increased from 11.8% to 80%, with a PPV and NPV of 66.67% and 99.26%, respectively (p<0.0001); and for rectal NETs the specificity increased from 97.6% to 99.3% and sensitivity raised from 7.1% to 66.7%, with a PPV and NPV of 80% and 98.53%, respectively (p<0.0001).

CONCLUSIONS

SATB2 stain is useful in differentiatingIslet1/PAX6 positive pancreatic and rectal NETs, as rectal NETs are typically moderately to strongly positive for SATB2 and pancreatic NETs are usually negative or weakly positive for SATB2. Moderate to strong staining for SATB2 is suggestive of an appendiceal or a rectal primary. SATB2 may complement the panel of CDX2, TTF1 and Islet1 in determining the site of origin of an NET in a metastatic setting.

Pathologic Considerations in Gastroenteropancreatic Neuroendocrine Tumors

This review serves as a primer on contemporary neuroendocrine neoplasm classification, with an emphasis on gastroenteropancreatic well-differentiated neuroendocrine tumors. Topics discussed include general features of neuroendocrine neoplasms, general neuroendocrine marker immunohistochemistry, the distinction of well-differentiated neuroendocrine tumor from pheochromocytoma/paraganglioma and other diagnostic mimics and poorly differentiated neuroendocrine carcinoma from diagnostic mimics, the concepts of differentiation and grade and the application of Ki-67 immunohistochemistry to determine the latter, the various WHO classifications of neuroendocrine neoplasms including the 2019 WHO classification of gastroenteropancreatic tumors, organ-specific considerations for gastroenteropancreatic well-differentiated neuroendocrine tumors, immunohistochemistry to determine site of origin in metastatic well-differentiated neuroendocrine tumor of occult origin, immunohistochemistry in the distinction of well-differentiated neuroendocrine tumor G3 from large cell neuroendocrine carcinoma, and, finally, required and recommended reporting elements for biopsies and resections of gastroenteropancreatic neuroendocrine epithelial neoplasms.

Immunohistochemistry in the diagnosis and classification of neuroendocrine neoplasms: what can brown do for you?

This review is based on a presentation given at the Hans Popper Hepatopathology Society companion meeting at the 2019 United States and Canadian Academy of Pathology Annual Meeting. It presents updates on the diagnosis and classification of neuroendocrine neoplasms, with an emphasis on the role of immunohistochemistry. Neuroendocrine neoplasms often present in liver biopsies as metastases of occult origin. Specific topics covered include 1. general features of neuroendocrine neoplasms, 2. general neuroendocrine marker immunohistochemistry, with discussion of the emerging marker INSM1, 3. non-small cell carcinoma with (occult) neuroendocrine differentiation, 4. the WHO Classification of neuroendocrine neoplasms, with discussion of the 2019 classification of gastroenteropancreatic neoplasms, 5. use of Ki-67 immunohistochemistry, 6. immunohistochemistry to assign site of origin in neuroendocrine metastasis of occult origin, 7. immunohistochemistry to distinguish well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma, 8. lesions frequently misdiagnosed as well-differentiated neuroendocrine tumor, and 9. required and recommended data elements for biopsies and resections with associated immunohistochemical stains. Next-generation immunohistochemistry, including lineage-restricted transcription factors (e.g., CDX2, islet 1, OTP, SATB2) and protein correlates of molecular genetic events (e.g., p53, Rb), is indispensable for the accurate diagnosis and classification of these neoplasms.

American Registry of Pathology Expert Opinions: Evaluation of poorly differentiated malignant neoplasms on limited samples - Gastrointestinal mucosal biopsies

This review reflects a collaboration between the American Registry of Pathology (the publisher of the Armed Forces Institute of Pathology Fascicles) and Annals of Diagnostic Pathology. It is part of a series of expert recommendations on topics encountered in daily practice. The authors, three pathologists with expertise in gastrointestinal tract pathology and immunohistochemistry, met on 30 July 2019 tasked with developing expert recommendations for evaluating poorly differentiated and undifferentiated malignant neoplasms encountered on mucosal biopsies of the gastrointestinal tract. We focused on esophageal, gastric, small intestinal, colorectal, and anal (i.e., tubal gut) samples. When faced with diagnostic uncertainty on the initial H&E, it is best to begin by trying to assign the broad tumor class with screening markers such as pankeratin, S100 protein or SOX10, and CD20 or CD45. Once a broad tumor class is established, more specific differentiation markers can be pursued (e.g., lineage-restricted transcription factors for adenocarcinoma; p40 for squamous cell carcinoma; chromogranin A and synaptophysin or INSM1 for neuroendocrine neoplasms). Every small biopsy containing tumor should be considered a potential molecular pathology sample; cutting extra unstained slides with this testing in mind is strongly encouraged.