INSM1, a Novel Biomarker for Detection of Neuroendocrine Neoplasms: Cytopathologists’ View

Head and Neck Fine Needle Aspiration: Current and Future Impact on Patient Care

The discovery of multiple novel biomarkers in head and neck tumors has led to an increasing interest in utilizing head and neck cytology material as the primary specimens for testing diagnostic and prognostic biomarkers. Although human papillomavirus and programmed death ligand 1 are the most well-established biomarkers tested in cytology specimens, their utilization in cytology is limited by the absence of standardized protocols for specimen collection and fixation. This has led to a quest for innovative techniques to explore the genomic landscape in head and neck tumors and its application in cytology.

Jumonji histone demethylases are therapeutic targets in small cell lung cancer

Small cell lung cancer (SCLC) is a recalcitrant cancer of neuroendocrine (NE) origin. Changes in therapeutic approaches against SCLC have been lacking over the decades. Here, we use preclinical models to identify a new therapeutic vulnerability in SCLC consisting of the targetable Jumonji lysine demethylase (KDM) family. We show that Jumonji demethylase inhibitors block malignant growth and that etoposide-resistant SCLC cell lines are particularly sensitive to Jumonji inhibition. Mechanistically, small molecule-mediated inhibition of Jumonji KDMs activates endoplasmic reticulum (ER) stress genes, upregulates ER stress signaling, and triggers apoptotic cell death. Furthermore, Jumonji inhibitors decrease protein levels of SCLC NE markers INSM1 and Secretogranin-3 and of driver transcription factors ASCL1 and NEUROD1. Genetic knockdown of KDM4A, a Jumonji demethylase highly expressed in SCLC and a known regulator of ER stress genes, induces ER stress response genes, decreases INSM1, Secretogranin-3, and NEUROD1 and inhibits proliferation of SCLC in vitro and in vivo. Lastly, we demonstrate that two different small molecule Jumonji KDM inhibitors (pan-inhibitor JIB-04 and KDM4 inhibitor SD70) block the growth of SCLC tumor xenografts in vivo. Our study highlights the translational potential of Jumonji KDM inhibitors against SCLC, a clinically feasible approach in light of recently opened clinical trials evaluating this drug class, and establishes KDM4A as a relevant target across SCLC subtypes.

The Significance of Insulinoma-Associated Protein 1 in the Pathological Diagnosis of Small-Cell Lung Cancer in Biopsy Specimens

Objective: Our purpose was to investigate the clinicopathological diagnostic value of immunohistochemical antibody for insulinoma-associated protein 1 (INSM1) in biopsy specimens of SCLC. Methods: Biopsy specimens of SCLC diagnosed at the pathology department of Tangshan Gongren Hospital from January 2022 to June 2023 were selected. INSM1 expression was detected and compared with conventional neuroendocrine markers synaptophysin (SYP), chromogranin A (CHGA), and CD56 regarding expression sensitivity and specificity. Results: The sensitivity of INSM1 expression was significantly higher than that of CHGA (95% vs 50%, P = .000), but there was no statistically significant difference in the specificity of INSM1, SYP, CHGA, and CD56 expression (100% vs 94% vs 98% vs 92%, respectively, P = .241, 1.000, .126). Conclusions: INSM1 antibody shows high sensitivity and specificity in the expression of SCLC and serves as a reliable immunohistochemical marker in the clinicopathological diagnosis of SCLC in biopsy specimens.

Primary Gastric Alveolar Rhabdomyosarcoma: A Potent Mimicker of Neuroendocrine Carcinoma

Alveolar rhabdomyosarcoma (ARMS) is a malignant tumor with skeletal muscle differentiation that usually occurs in soft tissues of the extremities or trunk. To date, only a few cases of primary gastric ARMS have been reported. Herein, we describe a case of ARMS in a man in his 80s and present a literature review. A submucosal tumor-like lesion was detected endoscopically. Histologically, the tumor cells exhibited a poorly differentiated morphology with hyperchromatic nuclei. Neuroendocrine markers, such as synaptophysin and CD56, were positive, and neuroendocrine carcinoma (NEC) was considered a differential diagnosis. However, both myogenic markers and OLIG2, which reflect FAX3 or FAX7 fusion, were positive, leading to a diagnosis of ARMS. Primary gastric ARMS is an extremely rare condition. Better awareness of this entity and its similarity to NEC is necessary for appropriate diagnosis and treatment.

Non-papillary thyroid carcinoma diagnoses in The Bethesda System for Reporting Thyroid Cytopathology categories V and VI: An institutional experience

BACKGROUND

The non-papillary thyroid carcinoma (PTC) subgroups of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) categories V (Suspicious for malignancy) and VI (Malignant) are rare, and specific tumor typing is difficult. We aimed to analyze histologic outcomes and to investigate the points of caution.

METHODS

We reviewed the electronic database and identified 12,215 cases of thyroid fine-needle aspiration cytology between 2013 and 2022. In total, 2783 patients were diagnosed with TBSRTC V or VI. Of these, 51 patients with non-PTC diagnosis were identified. Histological outcomes were analyzed with the cytologic findings.

RESULTS

The subgroups of non-PTC diagnoses in TBSRTC category V or VI consisted of medullary thyroid carcinoma (MTC) (13/51, 25.5 %), anaplastic thyroid carcinoma (3/51, 5.9 %), lymphoma (2/51, 3.9 %), metastatic tumor (4/51, 7.8 %), and malignant, not otherwise specified (NOS) (29/51, 56.9 %). The concordance rate of the histological outcomes was 30 % (12/40), predominantly comprising MTC cases. The obscuring factors for specific tumor typing in the suspicious for malignancy/malignant NOS cytology diagnosis group was mixed pattern of well differentiated thyroid carcinoma and less differentiated carcinoma cells (9/24, 37.5 %), low cellularity (7/24, 29.2 %) and a history of non-thyroid organ malignancy (6/24, 25 %). The less differentiated carcinoma component in mixed pattern consisted of 2 poorly differentiated thyroid carcinomas, 2 anaplastic thyroid carcinomas, 4 high-grade PTCs and 1 high-grade MTC.

CONCLUSION

The high-grade feature of PTC or MTC cytology is a noteworthy obscuring factor in specific tumor typing of non-PTC cytology diagnosis.

CytoLyt fixation impedes insulinoma-associated protein 1 (INSM1) immunoreactivity compared to formalin fixation

INTRODUCTION

Insulinoma-associated protein 1 (INSM1) is an immunohistochemical marker commonly used to confirm cytomorphological concordant neuroendocrine tumors/carcinomas (NETs/NECs), demonstrating high utility in small samples. Previous reports have suggested comparable INSM1 staining in CytoLyt-fixed cell blocks and formalin-fixed surgical pathology specimens. This study aimed to assess INSM1 immunoreactivity using both fixation methods and investigate potential factors contributing to its variable expression.

MATERIALS AND METHODS

A retrospective query was performed (03/31/21-05/31/22) for NET/NEC cases that had both formalin- and CytoLyt-fixed cell blocks. We collected clinical data and reporting of immunostains for each case. INSM1 staining was evaluated in both fixation methods, and reported as positive, negative, or equivocal. Equivocal INSM1 staining was further scored as a percentage of 1%-100% and intensity of weak (faint staining), moderate (darker staining), and strong (dense staining).

RESULTS

Our search identified 20 cases from diverse body sites, including mediastinal lymph nodes (40%), pancreas (35%), lung (20%), and porta hepatis lymph nodes (5%). All cases exhibited a widespread positivity (over 90%) in formalin-fixed cell blocks. In contrast, CytoLyt fixed cells showed a negative stain in 65% of cases and 30% exhibited an equivocal positivity.

CONCLUSIONS

While INSM1 is previously reported as a sensitive (75%-100%) and specific (82.7%-100%) marker for NET/NECs, our study found a reduced immunohistochemical staining in CytoLyt-fixed cell blocks. Consequently, false negative INSM1 immunohistochemical results in CytoLyt-fixed cell block material may pose a pitfall in the diagnosis of NET/NEC.

Recent Advances in Pathology of Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (ICCA) is a malignant epithelial neoplasm characterized by biliary differentiation within the liver. ICCA is molecularly heterogeneous and exhibits a broad spectrum of histopathological features. It is a highly aggressive carcinoma with high mortality and poor survival rates. ICCAs are classified into two main subtypes: the small-duct type and large-duct types. These two tumor types have different cell origins and clinicopathological features. ICCAs are characterized by numerous molecular alterations, including mutations in KRAS, TP53, IDH1/2, ARID1A, BAP1, BRAF, SAMD4, and EGFR, and FGFR2 fusion. Two main molecular subtypes-inflammation and proliferation-have been proposed. Recent advances in high-throughput assays using next-generation sequencing have improved our understanding of ICCA pathogenesis and molecular genetics. The diagnosis of ICCA poses a significant challenge for pathologists because of its varied morphologies and phenotypes. Accurate diagnosis of ICCA is essential for effective patient management and prognostic determination. This article provides an updated overview of ICCA pathology, focusing particularly on molecular features, histological subtypes, and diagnostic approaches.

Evaluation of immunohistochemical expression of novel neuroendocrine marker INSM1 and histological tumor growth pattern in well-differentiated neuroendocrine tumors of the appendix: 15-year single tertiary center experience

INTRODUCTION

Well-differentiated neuroendocrine tumors of the appendix (A-WDNET) are the most common neoplasms of the appendix but are rare and incidental. INSM1 is a novel transcription factor marker with high sensitivity and specificity for neuroendocrine differentiation. It may display architecturally diverse tumor growth patterns including solid, nest, insular trabecular, and acinar.

AIMS

The aim of this study was to determine the staining expression of INSM1 in A-WDNETs and detail the morphological tumor growth patterns.

MATERIALS AND METHODS

INSM1 immunohistochemistry was performed on 35 A-WDNET patients. Tumors were histologically classified according to their growth patterns.

RESULTS

Thirty-five patients, 60% of whom were male, had a mean age of 30 years at diagnosis and a mean tumor size of 0.9 cm. Eight percent of the tumors invaded the mucosa/submucosa, 34.3% showed invasion into the muscularis propria, 57.1% showed invasion into the subserosa or mesoappendix, LN metastasis was observed in two patients, lymph-vascular invasion in two patients, and perineural invasion in five patients. Ninety-four percent of the tumors were grade 1, the mitotic rate was >2% in two cases, and Ki-67 PI was >3% in two cases. INSM1 was positive in all cases (100%), 1+ 8.6%, 2+ 5.7%, 3+ 17.1%, 4+ 68.6%, weak staining in 11.4%, moderate staining in 22.9%, and strong staining in 67.7%. Type A histological growth pattern was observed in 54.3%, type B in 31.4%, and type C in 14.3% architecturally.

CONCLUSIONS

INSM1 was positive in all A-WDNET morphological patterns and was 100% sensitive. INSM1 IHC can be used as an alternative to traditional neuroendocrine markers or in combination with the diagnosis of neuroendocrine tumors.

Activity of the Ubiquitin-activating Enzyme Inhibitor TAK-243 in Adrenocortical Carcinoma Cell Lines, Patient-derived Organoids, and Murine Xenografts

Current treatment options for metastatic adrenocortical carcinoma (ACC) have limited efficacy, despite the common use of mitotane and cytotoxic agents. This study aimed to identify novel therapeutic options for ACC. An extensive drug screen was conducted to identify compounds with potential activity against ACC cell lines. We further investigated the mechanism of action of the identified compound, TAK-243, its synergistic effects with current ACC therapeutics, and its efficacy in ACC models including patient-derived organoids and mouse xenografts. TAK-243, a clinical ubiquitin-activating enzyme (UAE) inhibitor, showed potent activity in ACC cell lines. TAK-243 inhibited protein ubiquitination in ACC cells, leading to the accumulation of free ubiquitin, activation of the unfolded protein response, and induction of apoptosis. TAK-243 was found to be effluxed out of cells by MDR1, a drug efflux pump, and did not require Schlafen 11 (SLFN11) expression for its activity. Combination of TAK-243 with current ACC therapies (e.g., mitotane, etoposide, cisplatin) produced synergistic or additive effects. In addition, TAK-243 was highly synergistic with BCL2 inhibitors (Navitoclax and Venetoclax) in preclinical ACC models including patient-derived organoids. The tumor suppressive effects of TAK-243 and its synergistic effects with Venetoclax were further confirmed in a mouse xenograft model. These findings provide preclinical evidence to support the initiation of a clinical trial of TAK-243 in patients with advanced-stage ACC. TAK-243 is a promising potential treatment option for ACC, either as monotherapy or in combination with existing therapies or BCL2 inhibitors.

SIGNIFICANCE

ACC is a rare endocrine cancer with poor prognosis and limited therapeutic options. We report that TAK-243 is active alone and in combination with currently used therapies and with BCL2 and mTOR inhibitors in ACC preclinical models. Our results suggest implementation of TAK-243 in clinical trials for patients with advanced and metastatic ACC.

Cholangiocarcinoma: Pathologic and Molecular Classification in the Era of Precision Medicine

CONTEXT.—

Cholangiocarcinoma (CCA) is a heterogeneous cancer of the bile duct, and its diagnosis is often challenging.

OBJECTIVE.—

To provide insights into state-of-the-art approaches for the diagnosis of CCA.

DATA SOURCES.—

Literature review via PubMed search and authors' experiences.

CONCLUSIONS.—

CCA can be categorized as intrahepatic or extrahepatic. Intrahepatic CCA is further classified into small-duct-type and large-duct-type, whereas extrahepatic CCA is classified into distal and perihilar according to site of origin within the extrahepatic biliary tree. Tumor growth patterns include mass forming, periductal infiltrating, and intraductal tumors. The clinical diagnosis of CCA is challenging and usually occurs at an advanced tumor stage. Pathologic diagnosis is made difficult by tumor inaccessibility and challenges in distinguishing CCA from metastatic adenocarcinoma to the liver. Immunohistochemical stains can assist in differentiating CCA from other malignancies, such as hepatocellular carcinoma, but no distinctive CCA-specific immunohistochemical profile has been identified. Recent advances in next-generation sequencing-based high-throughput assays have identified distinct genomic profiles of CCA subtypes, including genomic alterations that are susceptible to targeted therapies or immune checkpoint inhibitors. Detailed histopathologic and molecular evaluations of CCA by pathologists are critical for correct diagnosis, subclassification, therapeutic decision-making, and prognostication. The first step toward achieving these goals is to acquire a detailed understanding of the histologic and genetic subtypes of this heterogeneous tumor group. Here, we review state-of-the-art approaches that should be applied to establish a diagnosis of CCA, including clinical presentation, histopathology, staging, and the practical use of genetic testing methodologies.

Neuroendocrine Marker Expression in Primary Non-neuroendocrine Epithelial Tumors of the Ovary: A Study of 551 Cases

Expression of neuroendocrine (NE) markers in primary ovarian non-NE epithelial tumors has rarely been evaluated. The aim of our study was to evaluate the expression of the most widely used NE markers in these neoplasms and to determine any prognostic significance of NE marker expression. The cohort consisted of 551 primary ovarian tumors, including serous borderline tumors, low-grade serous carcinomas, high-grade serous carcinomas (HGSC), clear cell carcinomas, endometroid carcinomas, mucinous borderline tumors, and mucinous carcinomas. Immunohistochemical analysis was performed using antibodies against INSM1, synaptophysin, chromogranin, and CD56 on tissue microarray. Positivity for INSM1, synaptophysin, chromogranin, and CD56 was most frequently observed in mucinous tumors (48.7%, 26.0%, 41.5%, and 100%, respectively). The positivity for these NE markers was mostly restricted to nonmucinous elements distributed throughout the tumor. The mucinous borderline tumor and mucinous carcinomas groups had similar proportions of positivity (mucinous borderline tumor: 53%, mucinous carcinomas: 39%). In the other tumor types, except for HGSC, there was only focal expression (5%-10%) or negativity for NE markers. HGSC showed high CD56 expression (in 26% of cases). Survival analysis was only performed for CD56 in HGSC as this was the only group with sufficient positive cases, and it showed no prognostic significance. Except for mucinous tumors, expression of NE markers in non-NE ovarian epithelial tumors is low. CD56 expression in HGSC occurs frequently but is without diagnostic or prognostic value.

The role of insulinoma-associated protein 1 in predicting the progression and prognosis of human olfactory neuroblastoma in China

OBJECTIVE

Recent studies have suggested that insulinoma-associated protein 1 (INSM1) is a useful marker for pathological diagnosis of neuroendocrine tumors. In the present study, we investigated the association between INSM1 expression and prognosis in patients with olfactory neuroblastoma (ONB) and assessed the usefulness of INSM1 as a prognostic biomarker in these patients.

METHOD

Immunohistochemistry was performed on 109 ONB patients who underwent endoscopic surgery at Beijing Tong Ren Hospital (Beijing, China) between June 2006 and November 2021 Patient age at the time of surgery ranged from 10 months to 72 years (mean age, 43.55 ± 13.47 years). In total, 63 (57.8%) and 46 (42.2%) tumors occurred in male and female patients, respectively. The percentages of grade I-IV cases were 13.8% (15/109), 36.7% (40/109), 29.4% (32/109) and 20.2% (22/109), respectively.

RESULTS

The expression rate (moderately/strongly positive) of INSM1 was significantly higher in high-grade (Ⅲ/Ⅳ; 83%; 45/54) than low-grade (Ⅰ/Ⅱ; 27%; 15/55) ONB cases. High expression levels of INSM1 were significantly positively associated with high pathological stage (p < 0.001), local recurrence, and death. Kaplan‑Meier analysis revealed that patients with high INSM1 expression had significantly shorter disease‑free survival (DFS) and mean survival (75.01 ± 10.71 vs. 158.56 ± 10.32) times, and shorter overall survival (OS). Multivariate Cox regression analysis revealed that INSM1 was an independent prognostic factor for DFS (HR: 4.963, 95%CI [2.11-10.84] p < 0.001) and OS (HR: 4.791, 95%CI [2.117-10.485], p < 0.001) after adjusting for sex, age, and tumor grade. In addition, INSM1 was an independent prognostic factor for DFS in patients treated with surgery (HR: 3.714, 95%CI [1.267-10.889], p = 0.017) and chemotherapy (HR: 5.574, 95%CI [1.584-19.612], p = 0.007).

CONCLUSION

INSM1 expression had a positive association with the prognosis of patients with ONB and could serve as a prognostic biomarker in these patients.

Well‑differentiated neuroendocrine tumor of the right kidney: A case report

Neuroendocrine tumors (NETs) are tumors originating from neuroendocrine cells and peptidergic neurons. Primary renal well-differentiated NETs (WDNETs) are rare and only sporadic cases have been reported worldwide. In November 2021, a 45-year-old female patient was admitted to The Affiliated Hospital of Zunyi Medical University (Zunyi, China) with right-sided lumbago. Abdominal computed tomography revealed a 44×34×70-mm mass in the right kidney. Following a complete examination, a laparoscopic partial nephrectomy of the right kidney was performed under general anesthesia. The postoperative pathology indicated a well-differentiated NET of the right kidney. There was no tumor recurrence or metastasis during the 1-year follow-up period. WDNETs are rare, their clinical and imaging findings are not specific, and their diagnosis depends on immunohistochemical analysis. The degree of malignancy is low and the prognosis is positive. Surgical resection is often the first choice, and long-term follow-up is required.

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.

[Whipple's triad with high and low insulin levels]

A 69-year-old female patient and a 70-year-old male patient were admitted to hospital with recurrent, severe hypoglycemic episodes and a typical manifestation of Whipple's triad. In the female, elevated levels of insulin, C‑peptide and pro-insulin together with pathological findings during a fasting test proved the presence of an insulinoma, which could be detected by Ga-68-DOTATOC-PET-CT in the pancreas. There was a very rare co-existence of a neuroendocrine Merkel cell carcinoma. In the male, levels of insulin and C‑peptide were suppressed and a diagnosis of paraneoplastic hypoglycemia by IGF‑2 secretion was made with increased glucose disposal in skeletal muscle proven by ¹⁸F‑FDG-PET-CT.

Unusual Microsatellite-Instable Mixed Neuroendocrine and Non-neuroendocrine Neoplasm: A Clinicopathological Inspection and Literature Review

BACKGROUND

Mixed neuroendocrine and non-endocrine neoplasms (MiNENs) are challenging to diagnose and manage clinically. The current understanding of MiNENs' pathobiology, molecular mechanisms, and management is incomplete. Though microsatellite instability (MSI) is known to impact carcinogenesis, reports examining MSI mechanisms for MiNENs are rare.

METHODS

We report an unusual colonic MSI-MiNEN uncovered in an 89-year-old woman and the review of the literature.

RESULTS

Pathologic inspection revealed a high-grade carcinoma composed of tumor cells with neuroendocrine histologic traits and immunophenotype intermixed with mucin-containing signet ring-like cells arranged in nested and micronodular patterns. Loss of MLH1 and PMS2 mismatch repair proteins was detected in tumor cells. INSM1 immunostaining highlighted about 50% of the tumour, further reinforcing the MiNEN diagnosis. Next-generation sequencing identified multiple carcinogenic mutations. Because of the advanced stage of the tumor and its adhesion to the adjacent organs, surgical resection was aborted; immunotherapy was initiated. The tumor is in remission 30 months following initiation of treatment, and the patient remains asymptomatic.

CONCLUSION

This unique MSI MiNEN was characterized by its immunohistochemical and molecular signatures and illustrated how correctly diagnosing MSI can strongly improve a patient's outcomes.

Cytological diagnosis of olfactory neuroblastoma at metastatic sites, with emphasis on role of insulinoma-associated protein 1 immunocytochemistry

BACKGROUND

Olfactory neuroblastoma (ONB) is a rare neuroectodermal tumor with a propensity for lymph node and distant metastases in a proportion of cases, presenting opportunities for cytological diagnosis. Insulinoma-associated protein 1 (INSM1) is a recently identified marker of neuroendocrine differentiation with higher sensitivity and specificity than traditional neuroendocrine immunostains used in diagnosis of ONB.

METHODS

Archival aspirates diagnosed as metastatic ONB were retrieved and reviewed for described characteristics of ONB. Spare direct smears with sufficient cellular material from each case were selected, if available, and immunocytochemistry for INSM1 was performed on the destained alcohol-fixed smears. INSM1 was also performed on non-neuroendocrine malignant round cell tumors (MRCT).

RESULTS

Seven fine needle aspirates (FNA) from five patients were identified, all of which showed a small round cell tumor with fine to coarse granular chromatin. Most cases had moderate to high cellularity, comprised of loosely cohesive clusters and dispersed cells. While two-cell pattern, nuclear streaking and moulding were frequent, background neuropil, fibrillary cytoplasm, and rosettes were uncommon. INSM1 immunostaining performed on spare direct smears showed strong positivity in 30%-100% of tumor cells (mean: 62%) in all aspirates tested (100%). In comparison with other immunostains, INSM1 showed more robust staining, and was easier to interpret. All non-neuroendocrine MRCTs were negative for INSM1.

CONCLUSION

Metatstatic ONB can resemble other small round cell tumors, as all the diagnostic features of ONB may not be readily evident. INSM1 immunocytochemistry has high sensitivity and specificity and can reliably be used as a single marker to support the cytomorphology for a confirmatory diagnosis of ONB, even on direct smears if a cell block is not available.

The Complex Histopathological and Immunohistochemical Spectrum of Neuroendocrine Tumors-An Overview of the Latest Classifications

Neuroendocrine neoplasms (NENs) originate from the neuroendocrine cell system, which may either take the shape of organoid cell aggregations or be composed of dispersed cells across various organs. Therefore, these tumors are heterogenous regarding the site of origin, functional status, degree of aggressiveness, and prognosis. When treating patients with neuroendocrine tumors, one of the most significant challenges for physicians is determining the correct tumor grade and thus classifying patients into risk categories. Over the years, the classification of these tumors has changed significantly, often causing confusion due to clinical, molecular, and immunohistochemical variability. This review aims to outline the latest NENs classifications regardless of their site of origin. Thus, an overview of the key histopathological and immunohistochemical characteristics of NENs could pave the way to validate possible predictive and prognostic markers and also guide the therapeutic conduct.

Interplay: The Essential Role between INSM1 and N-Myc in Aggressive Neuroblastoma

Simple Summary

Neuroblastoma (NB) is a cancer that starts in certain very early forms of nerve cells of the sympathetic nervous system, most often found in an embryo or fetus. Symptoms may include bone pain, an abdominal mass, frequent urination, limping, anemia, spinal cord weakness, or bruising of the eye area. N-Myc is a key driver of high-risk NB. An elevated expression of N-Myc often predicts a poorer prognosis, in both time to tumor progression and overall survival rate. We discovered a transcription factor, insulinoma-associated-1 (INSM1), as the downstream target gene of N-Myc. INSM1 has emerged as a novel NB biomarker that plays a critical role in facilitating NB tumor cell development. Both N-Myc and INSM1 demonstrate high clinical relevance to NB. Therefore, further understanding the association of INSM1 and N-Myc functions in aggressive NB should be beneficial for future NB treatment.

Abstract

An aggressive form of neuroblastoma (NB), a malignant childhood cancer derived from granule neuron precursors and sympathoadrenal lineage, frequently comprises MYCN amplification/elevated N-Myc expression, which contributes to the development of neural crest-derived embryonal malignancy. N-Myc is an oncogenic driver in NB. Persistent N-Myc expression during the maturation of SA precursor cells can cause blockage of the apoptosis and induce abnormal proliferation, resulting in NB development. An insulinoma-associated-1 (INSM1) zinc-finger transcription factor has emerged as an NB biomarker that plays a critical role in facilitating tumor cell growth and transformation. INSM1 plays an essential role in sympathoadrenal cell differentiation. N-Myc activates endogenous INSM1 through an E2-box of the INSM1 proximal promoter, whereas INSM1 enhances N-Myc stability via RAC-α-serine/threonine protein kinase (AKT) phosphorylation in NB. The ectopic expression of INSM1 stimulates NB tumor growth in contrast to the knockdown of INSM1 that inhibits NB cell proliferation. The clinical pathological result and bioinformatics analysis show that INSM1 is a strong diagnostic and a prognostic biomarker for the evaluation of NB progression. The INSM1/N-Myc expression shows high clinical relevance in NB. Therefore, targeting the INSM1/N-Myc-associated signaling axis should be a feasible approach to identifying new drugs for the suppression of NB tumor growth.

The Role of Epigenetic Change in Therapy-Induced Neuroendocrine Prostate Cancer Lineage Plasticity

The androgen receptor (AR) signaling pathway is critical for growth and differentiation of prostate cancer cells. For that reason, androgen deprivation therapy with medical or surgical castration is the principal treatment for metastatic prostate cancer. More recently, new potent AR signaling inhibitors (ARSIs) have been developed. These drugs improve survival for men with metastatic castration-resistant prostate cancer (CRPC), the lethal form of the disease. However, ARSI resistance is nearly universal. One recently appreciated resistance mechanism is lineage plasticity or switch from an AR-driven, luminal differentiation program to an alternate differentiation program. Importantly, lineage plasticity appears to be increasing in incidence in the era of new ARSIs, strongly implicating AR suppression in this process. Lineage plasticity and shift from AR-driven tumors occur on a continuum, ranging from AR-expressing tumors with low AR activity to AR-null tumors that have activation of alternate differentiation programs versus the canonical luminal program found in AR-driven tumors. In many cases, AR loss coincides with the activation of a neuronal program, most commonly exemplified as therapy-induced neuroendocrine prostate cancer (t-NEPC). While genetic events clearly contribute to prostate cancer lineage plasticity, it is also clear that epigenetic events-including chromatin modifications and DNA methylation-play a major role. Many epigenetic factors are now targetable with drugs, establishing the importance of clarifying critical epigenetic factors that promote lineage plasticity. Furthermore, epigenetic marks are readily measurable, demonstrating the importance of clarifying which measurements will help to identify tumors that have undergone or are at risk of undergoing lineage plasticity. In this review, we discuss the role of AR pathway loss and activation of a neuronal differentiation program as key contributors to t-NEPC lineage plasticity. We also discuss new epigenetic therapeutic strategies to reverse lineage plasticity, including those that have recently entered clinical trials.

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.