Insulinoma-associated protein 1 (INSM1) is a useful marker for pancreatic neuroendocrine tumor

A comparative study of INSM1 (clone MRQ70) immunoreactivity on CytoLyt® pretreated cytology and resection specimens of pancreatic neuroendocrine tumors

INTRODUCTION

Insulinoma-associated protein 1 (INSM1) is a newly characterized sensitive and specific immunohistochemical marker for neuroendocrine (NE) tumors. Whereas more traditional NE markers, such as chromogranin A and synaptophysin, are cytoplasmic, INSM1 is uniquely nuclear and thus could serve as a useful addition to NE tumor workup. While application of immunohistochemical studies to cytology specimens is becoming increasingly relevant, knowledge of the effects of the certain fixatives as well as the pattern and intensity of immunoexpression are important considerations.

METHODS

Sixteen cases of pancreatic neuroendocrine tumor (PanNET) diagnosed between 2015 and 2021 underwent both fine-needle aspiration, which was subsequently prepared in CytoLyt®-fixed cytology cell block (CCB), and surgical resection, in which specimens were prepared into formalin-fixed paraffin embedded blocks (FFPE). For all samples, INSM1 immunoreactivity was classified according to staining intensity and extent, then compared between CCBs and matched FFPEs.

RESULTS

All 16 FFPE specimens demonstrated strong and diffuse INSM1 immunoreactivity, while only 10/16 (62.5%) CCBs were positive. Of those 10, only 2/10 (20%) demonstrated strong and diffuse reactivity.

CONCLUSION

The choice of fixative has a demonstrable effect on the immunoreactivity of INSM1 in PanNET. Even though the sensitivity is lower in CytoLyt®-fixed cell block specimens, the addition of INSM1 is useful, especially in challenging cases that may be negative for one or more of the traditional NE markers.

INSM1 is a useful neuroendocrine marker to differentiate pancreatic serous cystadenoma from pancreatic well-differentiated neuroendocrine tumors in cytology and surgical specimens

INTRODUCTION

Differentiating pancreatic serous cystadenoma (SCA) from well-differentiated neuroendocrine tumors (WDNETs) based on histomorphology is critical yet challenging, particularly in small biopsy samples. Our study aimed to examine the expression profile of INSM1 in cytologic and surgical resection specimens from pancreatic SCA to evaluate its potential as a discriminative marker against pancreatic WDNET.

METHODS

We characterized INSM1 immunohistochemistry in 34 patients with pancreatic SCA, comprising 23 surgical resections and 11 cytology specimens. As a control, we used 28 cytology specimens from pancreatic WDNET. Clinical information was retrieved through a review of electronic medical records.

RESULTS

All 11 pancreatic SCA cytology specimens and 15 of 23 pancreatic SCA surgical resections exhibited absent INSM1 immunostaining. Each of the remaining eight surgical resection specimens demonstrated 1 % immunoreactivity. In contrast, 27 out of 28 (96 %) pancreatic WDNET cytology specimens were positive for INSM1 immunostaining, with a median immunoreactivity of 90 % and a range of 30-90 %. Overall, INSM1 immunostains perform similarly to chromogranin and synaptophysin in pancreatic SCA.

CONCLUSIONS

The results indicate that INSM1 immunohistochemistry staining may serve as a useful neuroendocrine marker to differentiate pancreatic SCA from pancreatic WDNET in clinical practice. To our knowledge, this represents the first large-scale study to evaluate INSM1 immunostaining in surgical and cytology specimens from pancreatic SCA.

Comparison of INSM1 immunostaining with established neuroendocrine markers synaptophysin and chromogranin A in over 14,000 neuroendocrine and non-neuroendocrine tumors

INSM1 is a transcription factor protein which is increasingly used as an immunohistochemical marker for neuroendocrine differentiation. To determine the prevalence of INSM1 expression in tumors and its expression pattern in normal tissues, tissue microarrays containing 14,908 samples from 117 different tumor types/subtypes as well as 76 different normal tissues were analyzed by immunohistochemistry. INSM1 was positive in 89.2% of 471 neuroendocrine neoplasms (NEN) and in 3.5% of 11,815 non-neuroendocrine neoplasms that were successfully analyzed. At least an occasional weak INSM1 positivity was observed in 59 different non-neuroendocrine tumor entities, of which 15 entities contained at least one case with strong INSM1 staining. A comparison with synaptophysin and chromogranin A staining revealed that in NEN, synaptophysin showed the highest sensitivity (93.3%), followed by INSM1 (89.2%) and chromogranin A (87.5%). In neuroendocrine carcinomas (NEC), sensitivity was highest for INSM1 (88.0%), followed by synaptophysin (86.5%) and chromogranin A (66.4%). If INSM1 was used as an additional marker, the sensitivity for detecting neuroendocrine differentiation in NEN increased from 96.6% (synaptophysin and chromogranin A) to 97.2% (synaptophysin, chromogranin A and INSM1). Our study shows that INSM1 is a useful additional marker for neuroendocrine differentiation with high sensitivity, particularly in NEC.

INSM1 expression in primary and metastatic neuroendocrine neoplasms at distinct locations

BACKGROUND

Insulinoma-associated protein 1 (INSM1) has been reported as a valuable marker for neuroendocrine neoplasms (NENs). The aims of this study were to evaluate any change in INSM1 expression between primary and metastatic NENs in distinct locations, as well as the expression of INSM1 at different differentiation levels. Furthermore, we would also investigate the significance of INSM1 expression in non-neuroendocrine neoplasms (non-NENs).

METHODS

We collected 78 cases with primary NENs and 16 cases with metastatic NENs. An addition 7 cases of non-NENs with neuroendocrine (NE) differentiation and 84 cases of other non-NENs, respectively, were included as controls.

RESULTS

In our cohort, 82% of primary NENs and 88% of metastatic NENs expressed INSM1 with no difference between them. There was no difference in the expression of INSM1 in the lung and digestive system, and its staining pattern was independent of tumor differentiation or location. The proportion of INSM1 -positive in non-NENs with NE differentiation was significantly higher than that in other non-NENs. INSM1 sensitivity for primary NENs (82%) was comparable to Chromogranin A (82%), less than that of Synaptophysin (96%) and CD56 (94%); specificity was higher (96% vs 94%, 82%, and 89%, respectively). The sensitivity of INSM1 for well differentiated NENs was significantly higher than that of poorly differentiated NENs (100% vs 79%).

CONCLUSIONS

INSM1 is a useful neuroendocrine marker in primary and metastatic NENs, helping to identify primary NENs with different degrees of differentiation. The expression of INSM1 was independent of tumor location. It should be with caution to interpret the expression of INSM1 in non-NENs that morphologically resemble NENs.

High expression of insulinoma-associated protein 1 (INSM1) distinguishes colorectal mixed and pure neuroendocrine carcinomas from conventional adenocarcinomas with diffuse expression of synaptophysin

Complementary to synaptophysin and chromogranin A, insulinoma-associated protein 1 (INSM1) has emerged as a sensitive marker for the diagnosis of neuroendocrine neoplasms. Since there are no comparative data regarding INSM1 expression in conventional colorectal adenocarcinomas (CRCs) and colorectal mixed adenoneuroendocrine carcinomas/neuroendocrine carcinomas (MANECs/NECs), we examined INSM1 in a large cohort of conventional CRCs and MANECs/NECs. In conventional CRC, we put a special focus on conventional CRC with diffuse expression of synaptophysin, which carry the risk of being misinterpreted as a MANEC or a NEC. We investigated INSM1 according to the immunoreactive score in our main cohort of 1,033 conventional CRCs and 21 MANECs/NECs in comparison to the expression of synaptophysin and chromogranin A and correlated the results with clinicopathological parameters and patient survival. All MANECs/NECs expressed INSM1, usually showing high or moderate expression (57% high, 34% moderate, and 9% low), which distinguished them from conventional CRCs, which were usually INSM1 negative or low, even if they diffusely expressed synaptophysin. High expression of INSM1 was not observed in conventional CRCs. Chromogranin A was negative/low in most conventional CRCs (99%), but also in most MANECs/NECs (66%). Comparable results were observed in our independent validation cohorts of conventional CRC (n = 274) and MANEC/NEC (n = 19). Similar to synaptophysin, INSM1 expression had no prognostic relevance in conventional CRCs, while true MANEC/NEC showed a highly impaired survival in univariate and multivariate analyses (e.g. disease-specific survival: p < 0.001). MANECs/NECs are a highly aggressive variant of colorectal cancer, which must be reliably identified. High expression of INSM1 distinguishes MANEC/NEC from conventional CRCs with diffuse expression of the standard neuroendocrine marker synaptophysin, which do not share the same dismal prognosis. Therefore, high INSM1 expression is a highly specific/sensitive marker that is supportive for the diagnosis of true colorectal MANEC/NEC.

Small Molecules Targeting INSM1 for the Treatment of High-Risk Neuroblastoma

Human neuroblastoma (NB) is the most common childhood extracranial tumor arising from the sympathetic nervous system. It is also a clinically heterogeneous disease that ranges from spontaneous regression to high-risk stage 4 disease. The cause of this disease remains elusive. However, the amplification of NMYC oncogene occurred in roughly 30% of NB patients, which strongly correlated with the advanced stage of disease subtype and the worse prognosis status. We discovered that N-Myc oncoprotein binds and activates INSM1, a zinc-finger transcription factor of neuroendocrine tumors. We also found that INSM1 modulates N-Myc stability mediated through PI3K/AKT/GSK3β signaling pathway. Therefore, INSM1 emerges as a critical co-player with N-Myc in facilitating NB tumor cell growth and sustaining the advanced stage of malignancy. Using an INSM1-promoter driven luciferase screening-platform, we have recently identified fifteen small molecules that negatively regulate INSM1 expression. Interestingly, the identified small molecules can be divided into four large groups of compounds such as cell signaling inhibitor, DNA/RNA inhibitor, HDAC inhibitor, and cardiac glycoside. These findings support the presence of a unique mechanism associated with INSM1 and N-Myc interplay, which is critical in regulating NB tumor cell growth. We discuss the feasibility of identifying novel or repurposing small molecules targeting INSM1 as a potential treatment option for high-risk NB.

Integrating Functional Imaging and Molecular Profiling for Optimal Treatment Selection in Neuroendocrine Neoplasms (NEN)

PURPOSE OF REVIEW

Gastroenteropancreatic NEN (GEP-NEN) are group of malignancies with significant clinical, anatomical and molecular heterogeneity. High-grade GEP-NEN in particular present unique management challenges.

RECENT FINDINGS

In the current era, multidisciplinary management with access to a combination of functional imaging and targeted molecular profiling can provide important disease characterisation, guide individualised management and improve patient outcome. Multiple treatment options are now available, and combination and novel therapies are being explored in clinical trials. Precision medicine is highly relevant for a heterogenous disease like NEN. The integration of dual-tracer functional PET/CT imaging, molecular histopathology and genomic data has the potential to be used to gain a more comprehensive understanding of an individual patient's disease biology for precision diagnosis, prognostication and optimal treatment allocation.

INSM1 Expression in Mesenchymal Tumors and Its Clinicopathological Significance

BACKGROUND

Insulinoma-associated protein 1 (INSM1) has been identified as a nuclear marker of neuroendocrine tumors. Although INSM1 appears to be a subtle and specific biomarker for neuroendocrine tumor, its expression and clinicopathological significance in mesenchymal tumors remain unclear.

METHODS

We analyzed INSM1 mRNA level in GEO database and conducted immunohistological staining to detect the expression of INSM1 on 576 mesenchymal tumors from pathology department of Tongji Hospital.

RESULTS

At transcription level, INSM1 expression in AITL (angioimmunoblastic T-cell lymphoma) was higher than their adjacent normal tissues as well as Hodgkin's lymphoma. Moreover, INSM1 expression in well-differentiated liposarcoma (WDLPS) was significantly higher than normal fat (P = 0.014) and dedifferentiated liposarcoma (DDLPS) (P = 0.0248). At protein level, the positive rate of INSM1 in AITL was 18/48 (47.4%), while in DDLPS was 9/20 (45%). INSM1 expression in AITL was significantly higher than Hodgkin's lymphoma (P = 0.008). And INSM1 expression in WDLPS was significantly lower than DDLPS (P = 0.015).

CONCLUSION

The combination of GEO data and immunohistochemistry data indicated that the expression level of INSM1 was higher in AITL compared with normal control, suggesting that INSM1 may be involved in pathogenesis of AITL. The abnormal expression of INSM1 was found in WDLPS, and the positive rate of INSM1 was higher in DDLPS than in WDLPS. INSM1 may be involved in the regulation of liposarcoma development. There were significant differences in the expression of INSM1 between AITL and Hodgkin's lymphoma and WDLPS and DDLPS. These findings may assist in the differential diagnosis of these tumors when common markers are difficult to identify, enriching the diagnostic index system of mesenchymal tumors.

From morphology to molecular targets—the pathologist’s view in diagnosing gastroenteropancreatic neuroendocrine neoplasms

In the last decade, a number of genetic alterations in gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) have been identified. In addition, differences in tumor morphology as well as proliferation index (Ki-67) or number of mitoses have led to changes in the classification of these neoplasms. According to the new World Health Organization (WHO) classification, GEP-NENs are now divided into two genetically and prognostically different categories: (i) well-differentiated neuroendocrine tumors (NET) subdivided into low (G1), intermediate (2) and high (G3) grade tumors, and (ii) poorly differentiated neuroendocrine carcinomas (NEC). In addition, a group of mixed neuroendocrine–non-neuroendocrine neoplasms (MiNEN) has been defined. This review focuses on the clinical, morphological, immunohistochemical and molecular findings of the GEP-NENs and their key diagnostic features that can help the pathologist to differentiate between tumors in this heterogeneous group. In challenging cases, additional immunohistochemical and/or molecular analysis can be helpful to determine the correct diagnosis and proper treatment for the patient.

Insulinoma-associated-1 (INSM1) expression in thymic squamous cell carcinoma

Thymic squamous cell carcinoma (TSC) presents distinct immunohistochemical features with its expression of CD5 and CD117, both of which are rarely expressed in squamous cell carcinoma in other organs. We found insulinoma-associated-1 (INSM1) expression in some TSCs; thus, a series of thymic tumors were examined retrospectively. Using surgically resected thymic tumors (TSC, n = 35; thymic atypical carcinoid [TAC], n = 4; and thymoma, n = 112) and non-neoplastic thymic tissue (n = 26), we evaluated immunohistochemically the expressions of INSM1, ASCL1, SOX2, NE markers (synaptophysin, chromogranin A, and CD56), and conventional TSC markers (CD5 and CD117). INSM1 was expressed in 22 TSCs (63%), whereas the positive frequencies of synaptophysin, chromogranin A, and CD56 were limited to 13, 10, and 1 cases, respectively. The discordance was highly contrasted with concordantly positive TACs. INSM1 and NE makers were rarely expressed in thymomas. INSM1 expression in TSCs was also associated with CD5 expression, which was significantly less frequent in INSM1-negative TSCs. INSM1, ASCL1, and SOX2 expressions were correlated with one another, but none of the single transcription factors or their combinations is associated with NE expression. The non-neoplastic medullary thymic epithelium was dispersedly positive for INSM1, particularly around Hassall's corpuscles. Despite positive INSM1, a significant decrease in the frequency of NE maker expression may present as a diagnostic pitfall in TSCs. Furthermore, the discordance, which was inherent in the non-neoplastic thymic epithelium, might be a characteristic feature in TSCs.

Synchronous or metachronous presentation of pancreatic neuroendocrine tumor versus secondary lesion to pancreas in patients affected by renal cell carcinoma. Systematic review

The simultaneous or metachronous occurrence of pancreatic neuroendocrine tumor (panNET) and renal cell carcinoma (RCC) may represent a rare coincidence or a manifestation of von Hippel-Lindau disease (VHL). These two malignancies share both radiological and cytopathological features, making the differential diagnosis very challenging. In this review, we collected all cases of concurrent diagnosis of localized panNET and RCC, with or without VHL, as reported in the literature to date. We aimed to provide an insight into the differential diagnosis between panNET and RCC pancreatic metastasis with a focus on the optimal therapeutic algorithm depending on the diagnosis. We performed literature research in PubMed library databases for articles about coexisting panNET and RCC published from 2001 to 2018. We selected nine articles with a total of 13 patients, including one treated at our institution. Patients' median age was 49 years and eight out of 13 patients were women. VHL was diagnosed in nine cases. Most patients underwent radical nephrectomy for RCC (9/13) and a clear cell renal carcinoma variant was identified in six cases. The diagnosis of panNET was synchronous with RCC detection in nine cases and metachronous in four cases. The diameter of the pancreatic lesion was >2 cm in six cases. In two cases the panNET was misdiagnosed as metastatic RCC by radiological tests. Somatostatin receptor scanning was performed only in our patient (Octreoscan) showing intense uptake in the pancreatic mass. Endoscopic ultrasound fine needle aspiration of the pancreatic lesion was performed in four patients: in two cases the panNET was confused with metastatic RCC by cytological analysis. Most patients underwent pancreatic surgery (10/13) without histological confirmation. Clear cell panNET was recognized in six cases, while mixed neuroendocrine non-neuroendocrine neoplasm was diagnosed in one patient. Immunohistochemistry (IHC) staining showed positivity to typical neuroendocrine markers (chromogranin A and synaptophysin) in all reported tested cases (8/8). Three patients underwent systemic treatment: two patients received sunitinib and one patient interleukin-2 (IL-2). Other neoplasms were observed in seven patients, of whom six were affected by VHL syndrome. When neoplastic lesions are recognized in both the kidney and pancreas, panNET and RCC pancreatic metastasis are often misdiagnosed due to similar radiological and cytopathological features. An accurate differential diagnosis is crucial and IHC plays a central role in distinguishing the two entities. The therapeutic algorithm may change depending on the diagnosis: while pancreatic RCC metastases benefit from resection, in panNETs and VHL the indication for surgery must be carefully evaluated.

Co-Expression of Adaptor Protein FAM159B with Different Markers for Neuroendocrine Cells: An Immunocytochemical and Immunohistochemical Study

Little is known about the adaptor protein FAM159B. Recently, FAM159B was shown to be particularly expressed in neuroendocrine cells and tissues, such as pancreatic islets and neuroendocrine cells of the bronchopulmonary and gastrointestinal tracts, as well as in different types of neuroendocrine tumours. To gain insights into possible interactions of FAM159B with other proteins and/or receptors, we analysed the co-expression of FAM159B and various neuroendocrine-specific markers in the cancer cell lines BON-1, PC-3, NCI-h82, OH-1, and A431 and also in human pancreatic tissues and pancreatic neuroendocrine tumours. The markers included prominent markers of neuroendocrine differentiation, such as chromogranin A (CgA), neuron-specific enolase (NSE), synaptophysin (SYP), insulinoma-associated protein 1 (INSM1), neural cell adhesion molecule 1 (NCAM1), serotonin (5-HT), somatostatin-14/28 (SST), and several receptors that are typically expressed by neuroendocrine cells, such as dopamine receptor 2 (D2R), somatostatin receptor (SSTR) 1, 2, 3, 4 and 5, and regulator of G-protein signalling 9 (RGS9). FAM159B was expressed evenly throughout the cytosol in all five cancer cell lines. Immunocytochemical and immunohistochemical analyses revealed co-expression of FAM159B with SYP, INSM1, RGS9, D2R, SSTR2, SSTR3, SSTR4, and SSTR5 and strong overlapping co-localisation with NSE. Double-labelling and co-immunoprecipitation Western blot analyses confirmed a direct association between FAM159B and NSE. These results suggest the involvement of FAM159B in several intracellular signalling pathways and a direct or indirect influence on diverse membrane proteins and receptors.

Insulinoma-Associated Protein 1 (INSM1): Diagnostic, Prognostic, and Therapeutic Use in Small Cell Lung Cancer

Small cell lung carcinoma (SCLC) is an aggressive and difficult to treat cancer. Although immunohistochemistry is not mandatory for a SCLC diagnosis, it might be required, especially in small samples. Insulinoma-associated protein 1 (INSM1) is expressed in endocrine and nervous tissues during embryogenesis, generally absent in adults and re-expressed in SCLC and other neuroendocrine neoplasms. Its high specificity propelled its use as diagnostic biomarker and an attractive therapeutic target. Herein, we aim to provide a systematic and critical review on the use of INSM1 for diagnosis, prognostication and the treatment of SCLC. An extensive bibliographic search was conducted in PubMed® focusing on articles published since 2015. According to the literature, INSM1 is a highly sensitive (75–100%) and specific (82–100%) neuroendocrine immunohistochemical marker for SCLC diagnosis. It can be used in histological and cytological samples. Although advantageous, its standalone use is currently not recommended. Studies correlating INSM1 expression and prognosis have disclosed contrasting results, although the expression seemed to entail a worse survival. Targeting INSM1 effectively suppressed SCLC growth either as a suicide gene therapy regulator or as an indirect target of molecular-targeted therapy. INSM1 represents a valuable biomarker for a SCLC diagnosis that additionally offers vast opportunities for the development of new prognostic and therapeutic strategies.

Immunohistochemical analyses of the expression profiles of INSM1, ATRX, DAXX and DLL3 in solid papillary carcinomas of the breast

Solid papillary carcinoma (SPC) is a rare but distinct clinicopathological feature of breast cancer characterised by frequent neuroendocrine differentiation. Insulinoma-associated protein 1 (INSM1) is a useful neuroendocrine marker for various neuroendocrine tumours. α-thalassemia/mental retardation syndrome X-linked protein (ATRX) and death domain-associated protein (DAXX) are useful prognostic markers for patients with pancreatic neuroendocrine tumours. However, to the best of our knowledge, few studies have addressed INSM1 expression in SPCs. Although ATRX, DAXX and δ-like canonical notch ligand 3 (DLL3) are frequently expressed in neuroendocrine lung carcinomas, there are no reports on their expression in SPCs. Therefore, the present study aimed to analyse the expression profiles of INSM1, ATRX, DAXX and DLL3 in the largest series of patients with SPC that has been, to the best of our knowledge, studied until now. Immunohistochemical analyses were performed to determine chromogranin A, synaptophysin, INSM1, ATRX, DAXX and DLL3 expression in 39 specimens surgically resected from patients with SPC (18 SPC in situ and 21 SPC invasive). The associations between the expression of these markers and the clinicopathological factors were investigated. Chromogranin A, synaptophysin and INSM1 were expressed in 64.1, 100 and 92.3% of the patients, respectively. Both ATRX and DAXX expression was observed in 28.2% of the patients. No patient expressed DLL3. Lack of INSM1 or chromogranin A expression was significantly associated with advanced pathological stages in patients with SPC (P=0.033) and in patients with invasive SPC (P=0.012), showing a tendency for a high Ki-67 labelling index (LI) and advanced histological grade in patients with invasive SPC. Loss of ATRX or DAXX expression was significantly associated with lymphatic invasion, but not with histological grade, Ki-67 LI or presence of invasive tumours. Thus, INSM1 was demonstrated to be a useful diagnostic marker for SPCs. Overall, detecting the lack of INSM1 or chromogranin A expression may be useful for analysing the characteristics of tumour cells in SPCs.

INSM1 Expression in Breast Neoplasms with Neuroedocrine Features

According to the 2019 WHO classification of breast tumors, neuroendocrine neoplasms (NENs) are classified into well-differentiated NE tumors (NET) and poorly differentiated NE carcinomas (NEC), while other breast cancers (BCs) of special and no special type with neuroendocrine (NE) features are not incorporated in this scheme anymore. We aimed to assess whether INSM1, a novel NE marker, could have a role in breast NEN subtyping. We selected 63 BCs operated from 2003 to 2018, classified as BCs with NE features, with available clinico-pathological data. Following 2019 WHO criteria, this cohort was reclassified into 37 NETs/NECs, the remaining 26 tumors representing solid-papillary (7), mucinous (7), and mixed type (12) carcinomas with NE differentiation. Chromogranin A (CGA) and synaptophysin (SYN) immunostains were reviewed, and INSM1 was tested by immunohistochemistry. Thirty CGA- and SYN-negative no special type BCs served as negative control. INSM1 was expressed in 52/63 cases of the whole cohort (82.54%). INSM1 positive and negative cases had no significantly different clinico-pathological characteristics. INSM1 expression was not significantly different between the newly reclassified NET/NEC group and other BCs with NE features. No immunoexpression was observed in control BCs. The sensitivity and specificity of INSM1 for the NE phenotype was 82.5% and 100%, respectively, compared to 61.9% and 100% for CGA, and 95.2 and 100% for SYN. In conclusion, INSM1 is as accurate as traditional NE biomarkers to identify NE differentiation in BC. In analogy to standard NE markers, INSM1 could not distinguish NET and NEC from the other BC histotypes with NE differentiation.

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

Background: Insulinoma-associated protein 1 (INSM1) has been considered as a novel immunostain for neuroendocrine tumors (NETs) and is hypothesized to be more reliable than first-generation NET biomarkers, such as CGA (chromogranin A), SYP (synaptophysin) and CD56 (neural cell adhesion molecule). In this review, we summarize existing literature on INSM1′s reliability as an immunostain for detection of various NETs, its results in comparison to first-generation NET biomarkers, and its expression in both non-NETs and benign tissues/cells on cytology specimens (cell blocks/smears).

Perspectives on the diagnostic, predictive and prognostic markers of neuroendocrine neoplasms (Review)

Neuroendocrine neoplasms (NENs) are a heterogeneous group of rare tumors with different types of physiology and prognosis. Therefore, prognostic information, including morphological differentiation, grade, tumor stage and primary location, are invaluable and contribute to the formulation of treatment decisions. Biomarkers that are currently used, including chromogranin A (CgA), serotonin and neuron-specific enolase, are singular parameters that cannot be used to accurately predict variables associated with tumor growth, including proliferation, metabolic rate and metastatic potential. In addition, site-specific biomarkers, such as insulin and gastrin, cannot be applied to all types of NENs. The clinical application of broad-spectrum markers, as it is the case for CgA, remains controversial despite being widely used. Due to limitations of the currently available mono-analyte biomarkers, recent studies were conducted to explore novel parameters for NEN diagnosis, prognosis, therapy stratification and evaluation of treatment response. Identification of prognostic factors for predicting NEN outcome is a critical requirement for the planning of adequate clinical management. Advances in ‘liquid’ biopsies and genomic analysis techniques, including microRNA, circulating tumor DNA or circulating tumor cells and sophisticated biomathematical analysis techniques, such as NETest or molecular image-based biomarkers, are currently under investigation as potentially novel tools for the management of NENs in the future. Despite these recent findings yielding promising observations, further research is necessary. The present review therefore summarizes the existing knowledge and recent advancements in the exploration of biochemical markers for NENs, with focus on gastroenteropancreatic-neuroendocrine tumors.

Neuroendocrine neoplasms of the pancreas: diagnosis and pitfalls

Common to neuroendocrine neoplasms of the pancreas is their expression of synaptophysin, chromogranin A, and/or INSM1. They differ, however, in their histological differentiation and molecular profile. Three groups can be distinguished: well-differentiated neuroendocrine neoplasms (neuroendocrine tumors), poorly differentiated neuroendocrine neoplasms (neuroendocrine carcinomas), and mixed neuroendocrine-non-neuroendocrine neoplasms. However, the expression of synaptophysin and, to a lesser extent, also chromogranin A is not restricted to the neuroendocrine neoplasms, but may also be in a subset of non-neuroendocrine epithelial and non-epithelial neoplasms. This review provides the essential criteria for the diagnosis of pancreatic neuroendocrine neoplasms including diagnostic clues for the distinction of high-grade neuroendocrine tumors from neuroendocrine carcinomas and an algorithm avoiding diagnostic pitfalls in the delineation of non-neuroendocrine neoplasms with neuroendocrine features from pancreatic neuroendocrine neoplasms.

Insulinoma-associated protein 1(INSM1) is a superior marker for the diagnosis of gastroenteropancreatic neuroendoerine neoplasms: a meta-analysis

PURPOSE

An increasing number of studies have shown that insulinoma-associated protein 1 (INSM1) is a robust marker for the diagnosis of gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN). The overall diagnostic accuracy of INSM1 for GEP-NEN remains unclear. The purpose of this study is to estimate the diagnostic value of INSM1 for GEP-NEN through a meta-analysis.

METHODS

We searched relevant studies addressing the accuracy of INSM1 in the diagnosis of GEP-NEN from PubMed, Web of Science, Embase, Cochrane Library and China National Knowledge Infrastructure (CNKI) as well as from reference lists since the establishment of the database to January 12, 2021. Pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and summary receiver operating characteristic (SROC) curves were used to comprehensively evaluate the diagnostic value of INSM1 for GEP-NEN. Statistical analysis was performed by Stata 15.0 and RevMan 5.4.

RESULTS

Nine studies with a total of 393 patients were included in the meta-analysis. The meta-analysis results showed that the pooled sensitivity and specificity of INSM1 for the diagnosis of GEP-NEN were 0.99 (95% CI: 0.87-1.00) and 0.96 (95% CI: 0.93-0.98), respectively. The PLR and NLR were 23.3 (95% CI: 13.3-40.8) and 0.01 (95% CI: 0.00-0.14), respectively. The DOR was 380.31 (95% CI: 164.14-881.21), and the area under the curve (AUC) of SROC curve was 0.98 (95% CI: 0.96-0.99).

CONCLUSIONS

The results show that INSM1 is an effective marker for the diagnosis of GEP-NEN with high sensitivity and specificity. INSM1 is recommended for clinical application to improve the diagnostic accuracy of GEP-NEN. However, more high-quality studies are needed to confirm these findings.

Insulinoma-associated Protein 1 (INSM1) Expression in Small Cell Neuroendocrine Carcinoma of the Urinary Tract

Clinical guidelines state that neoadjuvant chemotherapy should be administered before surgery in muscle invasive urinary bladder small cell neuroendocrine carcinoma. Recently described marker insulinoma-associated protein 1 (INSM1) has been reported to be sensitive and specific for neuroendocrine differentiation, however, its efficacy in urinary tract small cell carcinoma is not well established. This study examines immunohistochemical expression of INSM1 on whole tissue sections of urinary tract small cell neuroendocrine carcinoma and compares INSM1 expression with established neuroendocrine markers. Immunohistochemical stains for CD56, INSM1, synaptophysin, and chromogranin were performed on 32 cases of small cell neuroendocrine carcinoma of the bladder. Staining was scored for intensity (0: no staining; 1: weak; 2: moderate; 3: strong) and proportion of cells stained (0: 0%; 1: >0% to ≤25%; 2: >25% to ≤50%; 3: >50% to ≤75%; 4: >75% to 100%). INSM1 was positive (intensity 1 to 3 or proportion 1 to 4) in 87% (28/32) of cases (20 with intensity 2 to 3, 17 with proportion 3 to 4). CD56, synaptophysin, and chromogranin were positive in 75% (24/32), 60% (19/32), and 44% (14/32) of cases, respectively. INSM1 was negative (n=4) or only showed weak intensity staining (n=7) in 34% (11/32) of cases. INSM1 is a sensitive marker of small cell neuroendocrine differentiation of the urinary tract. However, this study suggests that optimal utilization of INSM1 would be inclusion in a limited panel of stains rather than as a stand-alone screening marker given that it is negative or only shows weak intensity staining in a significant proportion of cases.

Mesenchymal/non-epithelial mimickers of neuroendocrine neoplasms with a focus on fusion gene-associated and SWI/SNF-deficient tumors

Mimickers of neuroendocrine neoplasms (NEN) include a number of important pitfall tumors. Here, we describe our experience with mesenchymal mimics of NENs to illustrate their spectrum and draw the attention particularly to a group of mesenchymal/non-epithelial neoplasms (MN) that combine epithelioid histology with neuroendocrine (NE-) features and peculiar genetic abnormalities. In a consultation series of 4498 cases collected between 2009 and 2021, 2099 neoplasms expressing synaptophysin and/or chromograninA were reviewed and analyzed. A total of 364 (18%) were diagnosed as non-NENs, while the remaining tumors were NEN. The group of mesenchymal/non-epithelial neoplasms with NE-features (MN-NE) included 31/364 (8%) cases. These mostly malignant neoplasms showed an epithelioid morphology. While all but one tumor expressed synaptophysin, mostly patchy, only 10/29 (34%) co-expressed chromograninA. A total of 13/31 (42%) of the MN-NE showed EWSR1-related gene fusions (6 Ewing sarcomas, 5 clear cell sarcomas, and 1 desmoplastic small round cell tumor, 1 neoplasm with FUS-CREM gene fusion) and 7 (23%) were SWI/SNF (SMARCB1 or SMARCA4)-deficient neoplasms. The remaining MN-NE included synovial sarcoma, sclerosing epithelioid mesenchymal neoplasm, melanoma, alveolar soft part sarcoma, solitary fibrous tumor, and chordoma. A total of 27/31 MN-NE were from the last 8 years, and 6 of them were located in the pancreas. Eleven MN-NE were initially diagnosed as neuroendocrine carcinomas (NECs). MN-NE with epithelioid features play an increasing role as mimickers of NECs. They mostly belong to tumors with gene fusions involving the EWSR1 gene, or with SWI/SNF complex deficiency. Synaptophysin expression is mostly patchy and chromograninA expression is infrequent in MN-NE of this series and data extracted from literature.

Expression of insulinoma-associated protein 1 in non-small cell lung cancers: a diagnostic pitfall for neuroendocrine tumors

Insulinoma-associated protein 1 (INSM1) has been reported as a highly sensitive and specific marker of neuroendocrine tumors. INSM1 expression has also been reported, although uncommonly, in non-neuroendocrine tumors. This study aimed to elucidate potential nonspecific INSM1 expression in non-small cell non-neuroendocrine lung cancers (NSCNELCs), especially in squamous cell carcinomas (SqCCs) with basaloid features to avoid diagnostic pitfalls. Tissue microarrays (TMAs) were constructed for 324 NSCNELCs, including 196 adenocarcinomas (AdCs), 86 SqCCs, and 42 other NSCNELCs. In addition, 38 whole-tissue sections of SqCCs with basaloid features were examined. INSM1 immunostain was semiquantitively evaluated based on the percentage of nuclear staining in tumor cells, categorized as negative, focal (<10% tumor cells), and positive (>10% tumor cells). Among 324 TMAs, 6.2% (20/324) were positive for INSM1, 4.9% (16/324) were focal, and 88.9% (289/34) were negative. Of 196 AdCs, 5.1% (10/196) were positive for INSM1, 4.7% (9/196) were focal, and 90.3% (177/196) were negative. Of 86 SqCCs, 9.3% (8/86) were positive for INSM1, 5.8% (5/86) were focal, and 84.9% (73/86) were negative. Of the remaining 42 NSCNELCs, 4.8% (2/42) were positive for INSM1, 4.8% (2/42) were focal, and 90.4% (38/44) were negative. Among 38 cases of whole-tissue sections of SqCCs with basaloid features, 15.8% (6/38) were positive for INSM1, 18.4% (7/38) were focal, and 65.8% (25/38) were negative. Our study demonstrates that INSM1 is expressed in a significant subset of NSCNELCs, suggesting caution in interpreting INSM1 staining, especially with limited samples. INSM1 should not be used as a stand-alone neuroendocrine marker in differentiating primary lung tumors.

Insulinoma-associated Protein 1 (INSM1) in Thoracic Tumors is Less Sensitive but More Specific Compared With Synaptophysin, Chromogranin A, and CD56

OBJECTIVE

Recognition of neuroendocrine differentiation is important for tumor classification and treatment stratification. To detect and confirm neuroendocrine differentiation, a combination of morphology and immunohistochemistry is often required. In this regard, synaptophysin, chromogranin A, and CD56 are established immunohistochemical markers. Insulinoma-associated protein 1 (INSM1) has been suggested as a novel stand-alone marker with the potential to replace the current standard panel. In this study, we compared the sensitivity and specificity of INSM1 and established markers.

MATERIALS AND METHODS

A cohort of 493 lung tumors including 112 typical, 39 atypical carcinoids, 77 large cell neuroendocrine carcinomas, 144 small cell lung cancers, 30 thoracic paragangliomas, 47 adenocarcinomas, and 44 squamous cell carcinomas were selected and tissue microarrays were constructed. Synaptophysin, chromogranin A, CD56, and INSM1 were stained on all cases and evaluated manually as well as with an analysis software. Positivity was defined as ≥1% stained tumor cells in at least 1 of 2 cores per patient.

RESULTS

INSM1 was positive in 305 of 402 tumors with expected neuroendocrine differentiation (typical and atypical carcinoids, large cell neuroendocrine carcinomas, small cell lung cancers, and paraganglioma; sensitivity: 76%). INSM1 was negative in all but 1 of 91 analyzed non-neuroendocrine tumors (adenocarcinomas, squamous cell carcinomas; specificity: 99%). All conventional markers, as well as their combination, had a higher sensitivity (97%) and a lower specificity (78%) for neuroendocrine differentiation compared with INSM1.

CONCLUSIONS

Although INSM1 might be a meaningful adjunct in the differential diagnosis of neuroendocrine neoplasias, a general uncritical vote for replacing the traditional markers by INSM1 may not be justified.

A limited panel of INSM1 and LEF1 immunostains accurately distinguishes between pancreatic neuroendocrine tumor and solid pseudopapillary neoplasm

Solid pseudopapillary neoplasm (SPN) and well differentiated pancreatic neuroendocrine tumor (PNET) can show significant cytomorphological overlap. In this study, we evaluated the role of INSM1 and LEF1 immunohistochemical stains in distinguishing between these two tumors. 22 SPN and 25 PNET surgically resected cases were stained for both INSM1 and LEF1. All the 22 cases of SPN showed strong and diffuse nuclear staining for LEF1 (in >95 % of tumor cells), while all 25 PNET were negative for LEF1. All 25 PNET cases were positive for INSM1 (moderate to strong intensity nuclear staining in >50 % of the tumor cells), while all 22 cases of SPN were negative for INSM1. The results of our study show that a limited panel comprising of INSM1 and LEF1 immunostains accurately distinguishes between SPN and PNET.

INSM1 Is Less Sensitive But More Specific Than Synaptophysin in Gynecologic High-grade Neuroendocrine Carcinomas: An Immunohistochemical Study of 75 Cases With Specificity Test and Literature Review

Insulinoma-associated protein 1 (INSM1) has emerged as a promising diagnostic marker for high-grade neuroendocrine carcinomas (HGNECs); however, it is controversial whether INSM1 is more sensitive than conventional markers chromogranin, synaptophysin, and CD56. Here, we investigated immunohistochemical expression of INSM1 in 75 gynecologic HGNECs using full tissue sections (30 small-cell carcinomas [SmCCs], 34 large-cell neuroendocrine carcinomas [LCNECs], and 11 mixed SmCC and LCNEC), with specificity analysis in 422 gynecologic non-neuroendocrine tumors (410 in tissue microarrays and 12 full sections) and comparison with conventional neuroendocrine markers for their sensitivity and specificity. Positive INSM1 staining was seen in 69 (92%) HGNECs, whereas chromogranin, synaptophysin, and CD56 staining was seen in 61 (81%), 72 (96%), and 44 (69%) tumors, respectively (INSM1 vs. chromogranin, P=0.09; INSM1 vs. synaptophysin, P=0.4942; and INSM1 vs. CD56, P<0.001). The mean percentage of INSM1-positive tumor cells was 54% (median: 60%, range: 0% to 100%), similar to chromogranin (58%, P=0.2903) and higher than CD56 (30%, P=0.00001) but significantly lower than synaptophysin (89%, P<0.00001). INSM1 showed no staining difference among SmCCs, LCNECs, and mixed SmCC-LCNECs. Among the 422 non-neuroendocrine tumors, positive staining was seen in 5% tumors for INSM1, 18% for chromogranin, 19% for synaptophysin, and 25% for CD56. Our study indicates that INSM1 is a highly specific marker (95% specificity) for gynecologic HGNECs with high sensitivity (92%), but it is less sensitive than synaptophysin (96% sensitivity). INSM1 is more specific than chromogranin, synaptophysin, and CD56 for gynecologic HGNECs. Our literature review reveals that INSM1 has consistently (the same antibody clone A8 used for all reported studies) shown higher or similar sensitivity to chromogranin (for all 3 chromogranin antibody clones LK2H10, DAK-A3, DAKO polyclonal); however, whether INSM1 is more or less sensitive than synaptophysin or CD56 for HGNECs is highly dependent on the antibody clones used for synaptophysin (clones MRQ-40 and SNP88 showing higher sensitivity than clones 27G12 and DAK-SYNAP) or CD56 (clones CD564, MRQ-42, and MRQ-54 showing higher sensitivity than clones 123C3D5, 1B6, and Leu243).

Transcriptomics analysis for the identification of potential age-related genes and cells associated with three major urogenital cancers

Age is one of the most important risk factors of the occurrence for tumor patients. The majority of patients with urogenital cancers are the elderly, whose clinical characteristics are greatly affected by age and ageing. Our study aimed to explore age-related genes, cells, and biological changes in three common urogenital cancers via integrative bioinformatics analysis. First, mRNA (count format) and clinical data for bladder cancer, prostate cancer and renal cell carcinoma were downloaded from the Cancer Genome Atlas (TCGA). Through the comparison of clinicopathological characteristics, genes expression and cells infiltration between the old group and the young group, it was found that the clinical characteristics, genes and cells in the tumor microenvironment of different ages were quite different. And 4 key cells, 14 hub genes and some potential pathways were identified and considered as important factors. More importantly, we analyzed the differential landscape of the genes and cells from different perspectives, and confirmed its importance. In conclusion, we identified genes and cell types associated with age-related changes in the tumour microenvironment in urogenital cancer patients. These genes and cell types may play a critical role in the age-associated differences in clinicopathological characteristics among urogenital cancers, thus providing a link between ageing and cancer occurrence. The findings of this study may pave the way for the development of age-tailored approaches to treat cancer and other age-related diseases.

Effects of pharmacological calcimimetics on colorectal cancer cells over-expressing the human calcium-sensing receptor

The calcium-sensing receptor (CaSR) is a ubiquitously expressed multifunctional G protein-coupled receptor. Several studies reported that the CaSR plays an anti-inflammatory and anti-tumorigenic role in the intestine, and that it is down-regulated during colorectal carcinogenesis. We hypothesized that positive allosteric CaSR modulators (type II calcimimetics) selectively targeting the intestinal cells could be used for the treatment of intestinal pathologies. Therefore, the aim of this study was to determine the effect of pharmacological stimulation of CaSR on gene expression in vitro and on tumor growth in vivo. We stably transduced two colon cancer cell lines (HT29 and Caco2) with lentiviral vectors containing either the CaSR fused to GFP or GFP only. Using RNA sequencing, RT-qPCR experiments and ELISA, we determined that CaSR over-expression itself had generally little effect on gene expression in these cells. However, treatment with 1 μM of the calcimimetic NPS R-568 increased the expression of pro-inflammatory factors such as IL-23α and IL-8 and reduced the transcription of various differentiation markers in the cells over-expressing the CaSR. In vivo, neither the presence of the CaSR nor p.o. treatment of the animals with the calcimimetic cinacalcet affected tumor growth, tumor cell proliferation or tumor vascularization of murine HT29 xenografts. In summary, CaSR stimulation in CaSR over-expressing cells enhanced the expression of inflammatory markers in vitro, but was not able to repress colorectal cancer tumorigenicity in vivo. These findings suggest potential pro-inflammatory effects of the CaSR and type II calcimimetics in the intestine.

Clinical Routine Application of the Second-generation Neuroendocrine Markers ISL1, INSM1, and Secretagogin in Neuroendocrine Neoplasia: Staining Outcomes and Potential Clues for Determining Tumor Origin

Neuroendocrine neoplasms (NENs) have traditionally been identified via expression of proteins associated to the regulation of secretory vesicles and granules. We report the clinical usage of the "second-generation" proteins ISL LIM homeobox 1 (ISL1), INSM transcriptional repressor 1 (INSM1), and secretagogin (SECG) as immunohistochemical markers of neuroendocrine differentiation since their introduction in clinical routine and compare the results with the established proteins chromogranin A (CGA) and synaptophysin (SYP). In total, 161 tumors, including 139 NENs and 22 "non-NENs" (unrelated tumors with an initial suspicion of NEN), were informatively stained for ISL1, and subsets were also interrogated for INSM1 and/or SECG. Diffuse or focal positive immunoreactivity was noted for ISL1 in 91/139 NENs (65%) and in 6/22 (27%) non-NENs, for INSM1 in 76/85 NENs (89%) and in 2/5 (40%) non-NENs, and for SECG in 49 out of 64 NENs (77%) and in 0/5 non-NENs (0%). Generally, ISL1, INSM1, and SECG exhibited sensitivities in line with or slightly below that of CGA and SYP-largely attributable to tissue-specific patterns regarding tumoral origin. Moreover, for pancreatic and small intestinal NENs, the two largest subgroups, ISL1 staining results were consistent irrespectively of tumor source and WHO grade. We verify previously suggested immunohistochemical schemes of neuroendocrine markers of first- and second-generations to facilitate the diagnostic process for NENs and confirm that the second-generation neuroendocrine markers display tissue-specific patterns. We therefore recommend their implementation in tertiary endocrine pathology centers, not least to aid in the identification of primary tumors when analyzing metastases.

Modelling Pancreatic Neuroendocrine Cancer: From Bench Side to Clinic

Pancreatic neuroendocrine tumours (pNETs) are a heterogeneous group of epithelial tumours with neuroendocrine differentiation. Although rare (incidence of <1 in 100,000), they are the second most common group of pancreatic neoplasms after pancreatic ductal adenocarcinoma (PDAC). pNET incidence is however on the rise and patient outcomes, although variable, have been linked with 5-year survival rates as low as 40%. Improvement of diagnostic and treatment modalities strongly relies on disease models that reconstruct the disease ex vivo. A key constraint in pNET research, however, is the absence of human pNET models that accurately capture the original tumour phenotype. In attempts to more closely mimic the disease in its native environment, three-dimensional culture models as well as in vivo models, such as genetically engineered mouse models (GEMMs), have been developed. Despite adding significant contributions to our understanding of more complex biological processes associated with the development and progression of pNETs, factors such as ethical considerations and low rates of clinical translatability limit their use. Furthermore, a role for the site-specific extracellular matrix (ECM) in disease development and progression has become clear. Advances in tissue engineering have enabled the use of tissue constructs that are designed to establish disease ex vivo within a close to native ECM that can recapitulate tumour-associated tissue remodelling. Yet, such advanced models for studying pNETs remain underdeveloped. This review summarises the most clinically relevant disease models of pNETs currently used, as well as future directions for improved modelling of the disease.

Insulinoma-associated Protein 1 (INSM1) Is a Better Marker for the Diagnosis and Prognosis Estimation of Small Cell Lung Carcinoma Than Neuroendocrine Phenotype Markers Such as Chromogranin A, Synaptophysin, and CD56

To diagnose small cell lung carcinoma (SCLC), neuroendocrine (NE) phenotype markers such as chromogranin A, synaptophysin, and CD56 are helpful. However, because they are dispensable, SCLCs occur without apparent NE phenotypes. Insulinoma-associated protein 1 (INSM1) is a transcription factor for NE differentiation and has emerged as a single practical marker for SCLC. Using the surgical samples of 141 pulmonary NE tumors (78 SCLCs, 44 large cell NE carcinomas, and 19 carcinoids), and 246 non-NE carcinomas, we examined the immunohistochemical expression and prognostic relevance of INSM1 in association with NE phenotype markers. We evaluated its sensitivity and specificity for SCLC diagnosis, as well as its usefulness to diagnose SCLC without NE marker expression and to estimate the prognosis. INSM1 was expressed in SCLCs (92%, 72/78), large cell NE carcinomas (68%, 30/44), and carcinoids (95%, 18/19). In addition, among SCLCs with no expression of NE phenotype markers (n=12), 9 (75%) were positive for INSM1. These data suggest the superiority of INSM1 to the phenotype markers. Only 7% of adenocarcinomas (9/134) and 4% of squamous cell carcinomas (4/112) were positive for INSM1. SCLC with low-INSM1 expression (n=28) had a significantly better prognosis (P=0.040) than the high-INSM1 group (n=50). Our study revealed that INSM1 is highly sensitive and specific to detect SCLC and can estimate prognosis. INSM1 will be a promising marker for SCLC.

A promoter-driven assay for INSM1-associated signaling pathway in neuroblastoma

Aggressive form of neuroblastoma (NB) is a malignant childhood cancer derived from granule neuron precursors and sympatho-adrenal lineage with N-MYC amplification. An insulinoma associated-1 (INSM1) transcription factor has emerged as a NB biomarker that plays critical role in facilitating tumor cell growth and transformation. N-myc activates INSM1 in NB was discovered. In order to elucidate the signaling pathways associated with INSM1 expression and NB tumor cell growth, we developed an INSM1 promoter-driven luciferase assay for new drug discovery. Promoter-driven luciferase assay demonstrated high Z' factor (>0.7). Performance measures using signal-to-noise ratio, signal window, and Z' factor confirmed this assay is a robust screening method. A panel of FDA-approved oncology drugs set (147 compounds) was subjected to the INSM1 promoter-driven luciferase assay. The positive-hit compounds were validated for effects on cell viability and INSM1 expression. Screening a FDA-approved oncology drugs set revealed multiple inhibitors against various signaling pathways via suppression of INSM1 promoter activity. The positive-hit compounds consist of 9 signaling pathway inhibitors negatively regulates INSM1 expression and cell viability in NB. These inhibitors target DNA/RNA/protein synthesis, tubulin assembly, and histone deacetylase signaling pathways. The outcome of this assay indicates that the newly identified pathways could be critical for NB growth and transformation. This technology and the positive-hits of multiple pathways represent a promising option of identifying re-purposed FDA-approved drugs valuable for NB treatment in the context of a NB-specific marker, INSM1.

INSM1 is a novel prognostic neuroendocrine marker for luminal B breast cancer

Insulinoma associated protein 1 (INSM1) is a relatively new marker of neuroendocrine differentiation. It has been shown to have a high sensitivity for neuroendocrine tumours arising from different organs. This study evaluated INSM1 as a marker for neuroendocrine differentiation in infiltrating breast cancers (IBC). The expression of INSM1, together with other neuroendocrine markers (synaptophysin, chromogranin and CD56) was assessed in a large IBC cohort using tissue microarray by immunohistochemistry. Overall, 13.1%, 4.6%, 7.0% and 6.5% of the cases were positive for synaptophysin, chromogranin, INSM1 and CD56, respectively. INSM1 expression showed similar clinicopathological and biomarker profiles as chromogranin and synaptophysin. They were associated positively with luminal profile (p<0.001) and hormone receptors expression (p≤0.015), but negatively with HER2 (p≤0.044) and high molecular weight cytokeratins (p≤0.047). Using synaptophysin and/or chromogranin to define neuroendocrine differentiation, INSM1 showed a sensitivity of 37.3%, and was more sensitive than chromogranin (33.5%) and CD56 (16.4%) but less than synaptophysin (94.6%). Interestingly, INSM1 expression segregated IBC with neuroendocrine differentiation into different prognostic subgroups, particularly within luminal B subtype. Among the synaptophysin/chromogranin+ luminal B cancers, INSM1 expression was associated with significantly better survival (DFS: χ²=8.009, p=0.004; BCSS: χ²=3.873, p=0.049). Multivariate analysis showed that synaptophysin/chromogranin+ INSM1- status was an independent adverse factor for DFS (HR=2.282, 95%CI=1.196-4.356, p=0.012) in the luminal B subtype. Our data supported the usefulness of INSM1 in detecting neuroendocrine differentiation in IBC. Furthermore, INSM1 expression suggested a favourable prognostic impact; thus, it could be useful for stratifying neuroendocrine tumours with different prognosis.

Comparative performance of insulinoma-associated protein 1 (INSM1) and routine immunohistochemical markers of neuroendocrine differentiation in the diagnosis of endocrine mucin-producing sweat gland carcinoma

Endocrine mucin-producing sweat gland carcinoma (EMPSGC) is a rare cutaneous adnexal malignancy with predilection for the eyelids of older adults. It must be distinguished from metastatic adenocarcinomas of extracutaneous origin and from benign adnexal proliferations on partial samples when a solid growth component and mucin production are not evident. Thus, demonstration of neuroendocrine differentiation can help to ensure a correct diagnosis. Insulinoma-associated protein 1 (INSM1) is a novel neuroendocrine marker that has recently shown greater sensitivity than synaptophysin (SYN) and chromogranin (CHR) in the diagnosis of various neuroendocrine neoplasms. We compared the performance of these three markers across 10 examples of EMPSGC. All EMPSGCs expressed INSM1. Eight of ten were also immunoreactive for SYN; however, INSM1 staining was generally more intense and stained a greater proportion of the tumor cells. CHR staining was weak and focal in most cases. INSM1 staining was present in hidrocystoma-like components of cystic EMPSGC. These findings suggest that INSM1 may be more sensitive than SYN and CHR and thus valuable for establishing a diagnosis of EMPSGC.

Well-differentiated rectal neuroendocrine tumors: analysis of histology, including insulinoma-associated protein 1 expression, and biologic behavior, involving a large cohort of 94 cases

Well-differentiated rectal neuroendocrine tumors (R-NETs) are increasingly being detected by screening colonoscopy, commonly manifesting as polyps. Chromogranin A is frequently negative in R-NETs. Insulinoma-associated protein 1 (INSM1) is a novel transcription factor that has recently shown excellent sensitivity and specificity for neuroendocrine (NE) differentiation in various anatomic sites but has not been systematically evaluated in R-NET. A retrospective histologic review of all available R-NETs was performed and stained for INSM1 immunohistochemistry, as well as for Ki-67 and chromogranin A, if not already available. Clinical and follow-up information was obtained from the medical chart. A total of 94 R-NETs were included in our cohort. Of these, 82 (87%) were <10 mm in greatest dimension, and submucosal involvement was noted in 70 patients (74%). The tumors displayed a variety of histologic patterns, and the majority of the cases had intratumoral fibrosis (61%). Synaptophysin and INSM1 were reactive in 100% cases, whereas chromogranin A was reactive in 45% cases. The mean Ki-67 proliferative index was 1.6% (range: 0.5-5%). The median follow-up of the cohort was 30 months (80 cases, range: 3-226 months). Only three patients were identified with regional lymph node metastasis, all of which showed a tumor size ≥10 mm and had lymphovascular invasion (LVI). R-NETs in our fairly large cohort display an indolent biologic behavior without distant metastasis. Metastatic disease in lymph nodes was associated with tumor size and the presence of LVI, but not with the Ki-67 proliferative index. This is also the first systematic study documenting INSM1 as a highly sensitive NE marker in R-NET.

INSM1 expression in a subset of thoracic malignancies and small round cell tumors: rare potential pitfalls for small cell carcinoma

INSM1 is a diagnostic marker for neuroendocrine tumors originating in multiple anatomic sites. In the lung, INSM1 shows 76-97% sensitivity for neuroendocrine tumors overall. Our aim was to characterize INSM1 as a diagnostic marker for small cell carcinoma in the context of its epithelial, lymphoid, and mesenchymal morphologic mimics. Immunohistochemistry was performed on 231 tumors, including lung neuroendocrine tumors, nonneuroendocrine carcinomas of the thoracic cavity, diffuse large B-cell lymphomas, and small round cell sarcomas, using an anti-INSM1 mouse monoclonal antibody. Extent (0-100%) and intensity (1-3+) of nuclear INSM1 staining was multiplied in each case to calculate an H-score. Demographic and clinical information was obtained from the medical record. INSM1 had an overall sensitivity and specificity of 81.5% and 82.7% for small cell carcinoma, respectively, using a threshold established with a receiver operating characteristic curve. 40/48 (82.7%) small cell carcinomas were positive for INSM1, including 19/24 (79%) small cell carcinomas that were negative for chromogranin and synaptophysin. 5/5 carcinoids and 21/28 (75%) large cell neuroendocrine carcinomas showed INSM1 expression. Among nonneuroendocrine tumors, 7/38 (18%) lung adenocarcinomas, 2/17 (12%) lung squamous cell carcinomas, 4/10 (40%) thymic carcinomas, 4/12 (33%) adenoid cystic carcinomas, 1/19 (5%) diffuse large B-cell lymphomas, 4/11 (36%) alveolar rhabdomyosarcomas, and 4/23 (17%) Ewing sarcomas were positive for INSM1. No synovial sarcomas or desmoplastic small round cell tumors were positive. Weak, focal INSM1 expression alone is insufficient as a diagnostic marker for small cell carcinoma, but is sensitive and specific, easy to interpret in small biopsies, and makes a valuable addition to a diagnostic panel.

The North American Neuroendocrine Tumor Society Consensus Guidelines for Surveillance and Medical Management of Pancreatic Neuroendocrine Tumors

This article is the result of the North American Neuroendocrine Tumor Society consensus conference on the medical management of pancreatic neuroendocrine tumors from July 19 to 20, 2018. The guidelines panel consisted of medical oncologists, pathologists, gastroenterologists, endocrinologists, and radiologists. The panel reviewed a series of questions regarding the medical management of patients with pancreatic neuroendocrine tumors as well as questions regarding surveillance after resection. The available literature was reviewed for each of the question and panel members voted on controversial topics, and the recommendations were included in a document circulated to all panel members for a final approval.

Neuroendocrine Tumors of the Gastrointestinal Tract and Pancreas.Surg Pathol Clin. 2019;12:1021-1044. [PMID: 31672292 DOI: 10.1016/j.path.2019.08.007]

Neuroendocrine neoplasms (NENs) of the gastrointestinal (GI) tract and pancreas are a rare and heterogeneous group of neoplasms characterized by common cellular features as well as unique site-specific traits. GI and pancreatic NENs are much rarer than the more common adenocarcinomas arising at these sites. However, the incidences of GI and pancreatic NENs have increased significantly, particularly in the stomach and common site, followed by rectum, appendix, colon, and stomach. Pancreatic NENs are also uncommon, with fewer than 1 per 100,000, accounting for 1% to 2% of all pancreatic neoplasms.

Insulinoma-associated protein 1 immunostaining for various types of neuroendocrine tumors on FNA smears

BACKGROUND

Insulinoma-associated protein 1 (INSM1) has recently emerged as a reliable nuclear immunostaining marker for detecting neuroendocrine tumors (NETs) in paraffin-embedded surgical samples and cytologic cell blocks, but the reliability of INSM1 staining on cytologic smears is understudied. This study investigated the performance of INSM1 staining on cytologic smears for the detection of various NETs in comparison with chromogranin (CG) and synaptophysin (SYN).

METHODS

INSM1, CG, and SYN were stained on cytologic smears of 70 NETs, including 20 pancreatic NETs, 10 lung carcinoid tumors, 11 small cell lung carcinomas (SCLCs), 10 medullary thyroid carcinomas, 10 Merkel cell carcinomas, 4 thymic atypical carcinoid tumors, and 5 olfactory neuroblastomas. The detection rate, the percentage of positive cells, and the staining intensity were recorded.

RESULTS

The overall detection rate of INSM1 (94%) was higher than the rates of CG (79%) and SYN (89%). The detection rate of INSM1 was higher than the rates of CG and SYN in SCLC, Merkel cell carcinoma, and olfactory neuroblastoma; higher than the rate of CG and equal to the rate of SYN in pancreatic NETs and medullary thyroid carcinoma; equal to the rate of CG and higher than the rate of SYN in thymic atypical carcinoid tumors; and equal to the rate of CG and lower than the rate of SYN in lung carcinoid tumors. INSM1 staining was easier to interpret than CG and SYN staining, especially in high-grade NETs.

CONCLUSIONS

INSM1 can be reliably stained on cytologic smears and outperforms CG and SYN in the verification of clinically or radiologically suspected NETs.

INSM1 Is a Highly Specific Marker of Neuroendocrine Differentiation in Primary Neoplasms of the Gastrointestinal Tract, Appendix, and Pancreas

OBJECTIVES

INSM1 has been described as a sensitive and specific neuroendocrine marker. This study aims to compare INSM1 with traditional neuroendocrine markers in gastrointestinal neuroendocrine neoplasms.

METHODS

Retrospective review (2008-2018) was used to retrieve paraffin-embedded tissue from 110 gastrointestinal neuroendocrine neoplasms and controls that was subsequently stained with INSM1, synaptophysin, chromogranin, CD56, and Ki-67.

RESULTS

INSM1 was positive in 16 of 17 (94.1%) gastric, 17 of 18 (94.4%) pancreatic, 13 of 18 (72.2%) small bowel, 17 of 21 (81.0%) colonic, and 26 of 36 (72.2%) appendiceal tumors. INSM1 was positive in 58 of 70 (82.9%) well-differentiated neuroendocrine tumors, 17 of 20 (85.0%) poorly differentiated neuroendocrine carcinomas, 8 of 11 (72.7%) low-grade goblet cell adenocarcinomas (grade 1), and 6 of 9 (66.7%) high-grade goblet cell adenocarcinomas (grade 2/3). INSM1 sensitivity for neuroendocrine neoplasms (80.9%) was less than that of synaptophysin (99.1%), chromogranin (88%), and CD56 (95.3%); specificity was higher (95.7% vs 86.0%, 87.3%, and 86.0%, respectively).

CONCLUSIONS

INSM1 is a useful marker of neuroendocrine differentiation in gastrointestinal neuroendocrine and mixed neuroendocrine neoplasms. Compared with traditional neuroendocrine markers, INSM1 is less sensitive but more specific.

An Algorithmic Immunohistochemical Approach to Define Tumor Type and Assign Site of Origin

Immunohistochemistry represents an indispensable complement to an epidemiology and morphology-driven approach to tumor diagnosis and site of origin assignment. This review reflects the state of my current practice, based on 15-years' experience in Pathology and a deep-dive into the literature, always striving to be better equipped to answer the age old questions, "What is it, and where is it from?" The tables and figures in this manuscript are the ones I "pull up on the computer" when I am teaching at the microscope and turn to myself when I am (frequently) stuck. This field is so exciting because I firmly believe that, through the application of next-generation immunohistochemistry, we can provide better answers than ever before. Specific topics covered in this review include (1) broad tumor classification and associated screening markers; (2) the role of cancer epidemiology in determining pretest probability; (3) broad-spectrum epithelial markers; (4) noncanonical expression of broad tumor class screening markers; (5) a morphologic pattern-based approach to poorly to undifferentiated malignant neoplasms; (6) a morphologic and immunohistochemical approach to define 4 main carcinoma types; (7) CK7/CK20 coordinate expression; (8) added value of semiquantitative immunohistochemical stain assessment; algorithmic immunohistochemical approaches to (9) "garden variety" adenocarcinomas presenting in the liver, (10) large polygonal cell adenocarcinomas, (11) the distinction of primary surface ovarian epithelial tumors with mucinous features from metastasis, (12) tumors presenting at alternative anatomic sites, (13) squamous cell carcinoma versus urothelial carcinoma, and neuroendocrine neoplasms, including (14) the distinction of pheochromocytoma/paraganglioma from well-differentiated neuroendocrine tumor, site of origin assignment in (15) well-differentiated neuroendocrine tumor and (16) poorly differentiated neuroendocrine carcinoma, and (17) the distinction of well-differentiated neuroendocrine tumor G3 from poorly differentiated neuroendocrine carcinoma; it concludes with (18) a discussion of diagnostic considerations in the broad-spectrum keratin/CD45/S-100-"triple-negative" neoplasm.

Expression of novel neuroendocrine marker insulinoma-associated protein 1 (INSM1) in genitourinary high-grade neuroendocrine carcinomas: An immunohistochemical study with specificity analysis and comparison to chromogranin, synaptophysin, and CD56

Confirmation of genitourinary high-grade neuroendocrine carcinomas (GU-HGNECs) often requires immunohistochemical staining. Here we evaluated a novel neuroendocrine marker, insulinoma-associated protein 1 (INSM1), in GU-HGNECs with comparison to chromogranin, synaptophysin and CD56. Immunohistochemical expression of INSM1, chromogranin, synaptophysin, and CD56 was evaluated in 39 GU-HGNECs using full tissue sections [4 in kidney, 28 in urinary bladder, and 7 in prostate; 31 small cell carcinomas (SmCCs), 6 large cell neuroendocrine carcinomas (LCNECs), 2 mixed SmCC-LCNECs]. In 33 SmCCs/components, INSM1 showed similar sensitivity (93.9 %) to chromogranin (87.8 %), synaptophysin (93.9 %) and CD56 (87.8 %), and stained a similar percentage of tumor cells (52 %) to chromogranin (49 %) and CD56 (52 %), but lower than synaptophysin (87 %) (p < 0.0001). In 8 LCNECs/components, INSM1 is similar to chromogranin, synaptophysin or CD56 in sensitivity (62.5 %, 62.5 %, 75 %, 62.5 %, respectively) and the mean percentage of positively stained tumor cells (21 %, 44 %, 48 %, 37 %, respectively). INSM1 is more sensitive for SmCCs than LCNECs (93.9 % vs. 62.5 %, p = 0.015). INSM1 showed 97.4 % specificity upon analyzing 273 genitourinary non-neuroendocrine tumors on tissue microarrays. Our study indicates that INSM1 is a sensitive marker for genitourinary HGNECs with high specificity. For genitourinary SmCCs, INSM1 shows similar sensitivity to chromogranin, synaptophysin and CD56 but stains a lower percentage of tumor cells than synaptophysin. For genitourinary LCNECs, INSM1 showed similar sensitivity to chromogranin, synaptophysin and CD56. INSM1 is more sensitive for genitourinary SmCCs than LCNECs. Our result and literature review indicate that whether INSM1 is more sensitive than conventional neuroendocrine markers for HGNECs depends on the tumor primary sites.

Insulinoma-associated protein 1 (INSM1): a potential biomarker and therapeutic target for neuroendocrine tumors

BACKGROUND

Insulinoma-associated protein 1 (INSM1), a transcriptional regulator with a zinc-finger DNA-binding domain, has been validated as a cytoplasmic marker for neuroendocrine differentiation of tumor cells. Next to its abundant expression in the fetal pancreas, it is expressed in brain tumors, pheochromocytomas, medullary thyroid carcinomas, insulinomas and pituitary and small-cell lung carcinomas. INSM1 is not expressed in normal adult tissues and/or most non-neuroendocrine tumors. It regulates various downstream signaling pathways, including the Sonic Hedgehog, PI3K/AKT, MEK/ERK1/2, ADK, p53, Wnt, histone acetylation, LSD1, cyclin D1, Ascl1 and N-Myc pathways. Although INSM1 appears to be a subtle and specific biomarker for neuroendocrine tumors, its role in tumor development has remained unclear.

CONCLUSIONS

Here, we highlight INSMI expression, as well as its diagnostic significance and use as a therapeutic target in various neuroendocrine tumors. Targeting signaling pathways or gene expression alterations associated with INSM1 expression may be instrumental for the design of novel therapeutic strategies for neuroendocrine tumors.

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.

Insulinoma-associated protein 1 (INSM1) is a robust marker for identifying and grading pancreatic neuroendocrine tumors

BACKGROUND

Pancreatic neuroendocrine tumor (PNET) is a diagnostic challenge with limited samples in not only identification but grading. Prior studies have shown insulinoma-associated protein 1 (INSM1) to be a robust marker in identifying PNETs from other solid pancreatic tumors on resection specimens. In this study, we investigated the utility of INSM1 not only for identifying PNETs but also for grading in cell blocks (CBs) and surgical resections (SRs).

METHODS

A search for PNET cases between 2000 and 2019 identified 55 samples (26 CBs and 29 SRs) that were further separated into high (2 CBs, 3 SRs), intermediate (4 CBs, 7 SRs), and low (20 CBs, 19 SRs) grades based on their final pathology report and Ki-67 level. Immunohistochemical (IHC) staining for INSM1 (C-8, Santa Cruz Biotechnology [1:100]) was performed and quantified using an H score of 0 to 300. Non-PNET solid pancreatic tumors were compared and included acinar cell carcinoma, solid pseudopapillary neoplasm, and ductal adenocarcinoma.

RESULTS

All 55 cases of PNET demonstrated nuclear INSM1 staining. The average H scores for INSM1 staining of PNET were 254 and 252 in CB and SR, respectively. The H scores decreased with increasing tumor grade, with low-grade (G1), intermediate-grade (G2), and high-grade (G3) tumors showing average INSM1 H scores of 229 and 253, 266 and 253, and 30 and 33 in both CB and SR, respectively.

CONCLUSION

IHC with INSM1 plays a role in identifying and potentially grading PNETs.

Fibrous Extracellular Spheroids in an Endoscopic Ultrasound-Guided Pancreatic Fine Needle Aspiration Correlating to a Gyriform Pancreatic Endocrine Tumor with a Unique Cobblestone Pavement Growth Pattern

Pancreatic neuroendocrine neoplasms (PanNENs) are uncommon tumors. Fine needle aspiration (FNA) samples from PanNENs are typically of high cellularity and lack necrosis. In cytology slides from these tumors, dyscohesive cells are usually reported with variably round to oval to plasmacytoid forms exhibiting coarsely granular chromatin and showing immunoreactivity for synaptophysin. We present an unusual, and to our knowledge not previously described, example of an FNA of a PanNEN with large extracellular fibrous spheroids containing intrinsic fibroblasts and rimmed by small to intermediate sized neoplastic epithelial cells with high nuclear cytoplasmic ratios. The cytomorphology of the PanNEN in this case was in some ways reminiscent of that expected in adenoid cystic carcinomas of the salivary glands that most often contain large extracellular globules of basement membrane material and a somewhat biphasic population of lesional cells. The cytomorphology in this case was found to correlate well with the resection specimen histomorphology of an exaggerated gyriform pattern of growth resulting in a unique cobblestone-pavement like microscopic appearance. Knowledge of this potential cytomorphology will aid the cytology community through recognition and reporting of this previously undescribed pattern in an uncommon disease.

RNA binding protein HuD and microRNA-203a cooperatively regulate insulinoma-associated 1 mRNA

RNA binding protein HuD regulates translation and turnover of target mRNAs, thereby affecting gene expression at the posttranscriptional level in mainly neuronal as well as pancreatic β-cells. Here, we identified insulinoma-associated 1 (INSM1), an essential factor governing differentiation and proliferation of neuroendocrine cells, as a novel target of HuD and demonstrated the regulatory mechanism of INSM1 expression by HuD. HuD bound to 3'untranslated region (3'UTR) of Insm1 mRNA and negatively regulated its expression; knockdown of HuD increased INSM1 expression, while HuD overexpression repressed it by destabilizing its mRNA. In addition, we further demonstrated that HuD enhanced reduction of INSM1 by miR-203a, a novel miRNA targeting Insm1 mRNA 3'UTR. These results suggest that HuD and miR-203a cooperatively regulate INSM1 expression and it provides a novel regulatory mechanism of INSM1 expression by HuD and miR-203a.

Insulinoma-associated protein 1 is a sensitive and specific marker for lung neuroendocrine tumors in cytologic and surgical specimens

INTRODUCTION

Insulinoma-associated protein 1 (INSM1) is an immunohistochemical marker for neuroendocrine differentiation with potentially superior sensitivity and specificity. INSM1 performance in pulmonary cytology cell block material (CB) has not been well established, and large series demonstrating its performance have been few.

MATERIALS AND METHODS

Typical and atypical carcinoid, small cell lung carcinoma, and large cell neuroendocrine carcinoma, squamous cell carcinoma, and adenocarcinoma CBs and 563 surgical specimens comprising 17 typical carcinoid, 14 atypical carcinoid, 8 small cell lung carcinoma, 10 large cell neuroendocrine carcinoma, 58 squamous cell carcinoma, 415 adenocarcinoma, and 17 large cell carcinoma cases and 24 other tumor types were immunostained with INSM1, CD56, synaptophysin, and chromogranin A.

RESULTS

The INSM1 sensitivity, specificity, positive predictive value, and negative predictive value were 92.3%, 100%, 78.9%, and 99% in the CBs and 89.8%, 98.1%, 81.5%, and 99% in the surgical specimens, respectively, with 86.2% concordance. The sensitivity, specificity, positive predictive value, and negative predictive value for the other neuroendocrine markers were 97.4%, 93.3%, 97.4%, and 93.3% in the CBs and 93.9%, 93.6%, 58.2%, and 99.4% in the surgical specimens for CD56; 89.7%, 100%, 100%, and 75% in the CBs and 93.4%, 91.2%, 50.5%, and 99.4% in the surgical specimens for synaptophysin; 66.7%, 100%, 100%, and 53.6% in the CBs and 75.5%, 98.6%, 84.1%, and 97.7% in the surgical specimens for chromogranin A, respectively. Finally, INSM1, together with CD56, maximized the sensitivity to 100% with 93.3% specificity in the CBs.

CONCLUSIONS

The results from our study have further established the high sensitivity and specificity of INSM1 in the largest pulmonary cytologic and surgical cohorts to date. INSM1 either matched or outperformed the performance of existing neuroendocrine markers, and its combination with CD56 appeared to maximize test performance.

INSM1 Expression in Peripheral Neuroblastic Tumors and Other Embryonal Neoplasms

Insulinoma-associated protein 1 (INSM1) is a transcription factor that functions in neuroepithelial tissue development and shows expression in neuroendocrine neoplasms. Given the role of INSM1 in controlling differentiation of the sympatho-adrenal lineage, we hypothesized that INSM1 expression would define a subset of neuroblastic tumors. This study aimed to characterize the immunohistochemical profile of INSM1 in a cohort of peripheral neuroblastic tumors and compare INSM1 expression in these tumors to that seen in other embryonal neoplasms, using both tissue microarrays and whole-slide histologic sections. INSM1 showed nuclear expression in 39/50 (78%) peripheral neuroblastic tumors, including 27/32 (84%) neuroblastomas, 9/9 (100%) ganglioneuroblastomas, and 3/9 (33%) ganglioneuromas. Altogether, 70% of peripheral neuroblastic tumors showed anti-INSM1 immunoreactivity in more than 20% of tumor nuclei. Although no non-neuroblastic tumors in this study exhibited INSM1 expression in more than 20% of nuclei, focal or patchy staining was identified in 7/14 (50%) rhabdomyosarcomas, 7/22 (32%) nephroblastomas, and 4/20 (20%) Ewing sarcomas. The absence of INSM1 expression in peripheral neuroblastic tumors was restricted to undifferentiated and poorly differentiated neuroblastomas, as well as mature ganglioneuromas, mimicking the transient INSM1 expression seen in sympatho-adrenal differentiation during normal development. No significant association between MYCN amplification status and INSM1 expression was observed. We found that all 3 INSM1-negative neuroblastoma patients with available follow-up were alive at a median of 15 years, in comparison to 9 of 13 INSM1-positive neuroblastoma patients living at a median of 5 years. Additional studies are needed to determine whether INSM1 expression is indicative of a clinically significant differentiation state in neuroblastoma.