CDX-2 Homeobox Gene Product Expression in Neuroendocrine Tumors

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

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

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

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

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

Renal neuroendocrine tumors: clinical and molecular pathology with an emphasis on frequent association with ectopic Cushing syndrome

Renal neuroendocrine tumors (RenNETs) are rare malignancies with largely unknown biology, hormone expression, and genetic abnormalities. This study aims to improve our understanding of the RenNETs with emphasis of functional, hormonal, and genetic features. Surgically resected RenNETs (N = 13) were retrieved, and immunohistochemistry and next-generation sequencing (NGS) were performed in all cases. In addition, all published RenNETs were systematically reviewed. Our cohort (4 men and 9 women, mean age 42, mean tumor size 7.6 cm) included 2 patients with Cushing syndrome (CS). WHO grade (23% G1, 54% G2, and 23% G3) and tumor progression did not correlate. CS-associated RenNETs (CS-RenNETs) showed a solid and eosinophilic histology and stained for ACTH, while the remaining non-functioning tumors had a trabecular pattern and expressed variably hormones somatostatin (91%), pancreatic polypeptide (63%), glucagon (54%), and serotonin (18%). The transcription factors ISL1 and SATB2 were expressed in all non-functioning, but not in CS-RenNETs. NGS revealed no pathogenic alterations or gene fusions. In the literature review (N = 194), 15 (8%) of the patients had hormonal syndromes, in which CS being the most frequent (7/15). Large tumor size and presence of metastasis were associated with shorter patients' survival (p < 0.01). RenNETs present as large tumors with metastases. CS-RenNETs differ through ACTH production and solid-eosinophilic histology from the non-functioning trabecular RenNETs that produce pancreas-related hormones and express ISL1 and SATB2. MEN1 or DAXX/ARTX abnormalities and fusion genes are not detected in RenNETs, indicating a distinct yet unknown molecular pathogenesis.

Histopathological Evaluation and Molecular Diagnostic Tests for Peritoneal Metastases with Unknown Primary Site-a Review

Cancer of unknown primary (CUP) is a well-studied entity with guidelines available for the management of patients with CUP. The peritoneum represents one of the metastatic sites in CUP, and peritoneal metastases (PM) could present as CUP. PM of unknown origin remains a poorly studied clinical entity. There is only one series of 15 cases, one population-based study, and few other case reports on this subject. Studies on CUP, in general, cover some common tumour histological types like adenocarcinomas and squamous carcinomas. Some of these tumours may have a good prognosis though majority have high-grade disease with a poor long-term outcome. Some of the histological tumour types commonly seen in the clinical scenario of PM like mucinous carcinoma have not been studied. In this review, we divide PM into five histological types-adenocarcinomas, serous carcinomas, mucinous carcinomas, sarcomas and other rare varieties. We provide algorithms to identify the primary tumour site using immunohistochemistry when imaging, and endoscopy fails to establish the primary tumour site. The role of molecular diagnostic tests for PM or unknown origin is also discussed. Current literature on site-specific systemic therapy based on gene expression profiling does not show a clear benefit of this approach over empirical systemic therapies.

Immunoexpression of CDX2 in metastatic nonintestinal adenocarcinomas: an immunohistochemical pitfall and its pathological implications

Background

CDX2, a homeobox gene is the marker of intestinal differentiation. Its expression may lead to misdiagnosis while evaluating metastasis from unknown primary. In the present narrative, we discuss the clinical, morphological, and immunohistochemical (IHC) findings of metastatic adenocarcinoma of the lymph node that displayed nuclear immunoexpression of CDX2. However, the clinical and radiological picture supported the non-intestinal primary; prostate in one and lung in the other.

Case presentation

A 68-year-old man presented cervical lymph node enlargement. An epithelial tumor with acinar and cribriform pattern was seen that showed expression of CK, CDX2, and PSA in IHC. The patients complained of nonspecific symptoms related to both the gastrointestinal system and the prostate. Serum PSA was diagnostic (> 500 ng/ml). Similarly, core biopsy from mediastinal lymph node from a 51-year-male was received with possible differential of cancer and tuberculosis. Moderately differentiated adenocarcinoma was observed with the expression of EMA, CK 7, CDX2, and TTF1. The expression of both CDX2 and TTF1 was patchy. When the patient was called and all the details were sought the computed tomography (CT) thorax showed a lower chest wall lesion and multiple metastasis. The case was hence signed off as primary from lung on basis of clinical picture.

Conclusion

Such deviants must be reported and recorded. The knowledge of these will make a pathologist cautious and thus avoid misdiagnosis.

Metastatic Neuroendocrine Neoplasms of Unknown Primary: Clues from Pathology Workup

Simple Summary

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

Abstract

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

mRNA profiling of a well-differentiated G1 pancreatic NET correlates with immunohistochemistry profile: a case report

Background

Neuroendocrine neoplasms (NENs) are a complex group of tumours that occur in many organs. Routinely used IHC markers for NEN diagnosis include CgA, synaptophysin, Ki67 and CD56. These have limitations including lack of correlation to clinical outcomes and their presence in non-tumour tissue. Identification of additional markers and more quantitative analyses of tumour tissue has the potential to contribute to improved clinical outcomes. We used qRT-PCR to profile the expression levels of a panel of markers in tumour and matched non-tumour tissue from a patient with a G1 pancreatic neuroendocrine tumour. Differences in mRNA levels between tumour and non-tumour tissue were compared with IHC analyses of the same sample.

Case presentation

An elderly man presented with lower abdominal pain for 6 months. Histological analysis identified a low grade, well differentiated pancreatic endocrine neoplasm. Twenty-seven tumour markers for neuroendocrine status, proliferation, stem cell phenotype, angiogenesis, epithelial to mesenchymal transition, cell adhesion, differentiation and tumour suppression were selected from previous studies and mRNA levels of these markers were measured in tumour and adjacent non-tumour tissue sample using qRT-PCR. IHC was carried out on the same tissue to detect the corresponding marker proteins. Of the markers analysed, seven showed higher mRNA levels in tumour relative to non-tumour tissue while thirteen had lower expression in tumour relative to non-tumour tissue. Substantial differences in mRNA levels were a gain of CgA, CD56, β-catenin, CK20, PDX1 and p53 and loss of Ki67, PCAD, CK7, CD31, MENA, ECAD, EPCAM, CDX2 and CK6. Comparison of qRT-PCR data with IHC showed correlation between fifteen markers.

Conclusion

Our study is unique as it included matched controls that provided a comparative assessment for tumour tissue analysis, whereas many previous studies report tumour data only. Additionally, we utilised qRT-PCR, a relatively quantitative diagnostic tool for differential marker profiling, having the advantage of being reproducible, fast, cheap and accurate. qRT-PCR has the potential to improve the defining of tumour phenotypes and, in combination with IHC may have clinical utility towards improving tumour stratification or distinguishing tumour grades. The results need to be validated with different grades of NENs and related to clinical outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-01705-9.

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

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

Cancer of Unknown Primary: Challenges and Progress in Clinical Management

Simple Summary

Patients with cancer of unknown primary site suffer the burden of an uncertain disease, which is characterized by the impossibility to identify the tissue where the tumor has originated. The identification of the primary site of a tumor is of great importance for the patient to have access to site-specific treatments and be enrolled in clinical trials. Therefore, patients with cancer of unknown primary have reduced therapeutic opportunities and poor prognosis. Advancements have been made in the molecular characterization of this tumor, which could be used to infer the tumor site-of-origin and thus broaden the diagnostic outcome. Moreover, we describe here the novel therapeutic opportunities that are based on the genetic and immunophenotypic characterization of the tumor, and thus independent from the tumor type, which could provide most benefit to patients with cancer of unknown primary.

Abstract

Distant metastases are the main cause of cancer-related deaths in patients with advanced tumors. A standard diagnostic workup usually contains the identification of the tissue-of-origin of metastatic tumors, although under certain circumstances, it remains elusive. This disease setting is defined as cancer of unknown primary (CUP). Accounting for approximately 3–5% of all cancer diagnoses, CUPs are characterized by an aggressive clinical behavior and represent a real therapeutic challenge. The lack of determination of a tissue of origin precludes CUP patients from specific evidence-based therapeutic options or access to clinical trial, which significantly impacts their life expectancy. In the era of precision medicine, it is essential to characterize CUP molecular features, including the expression profile of non-coding RNAs, to improve our understanding of CUP biology and identify novel therapeutic strategies. This review article sheds light on this enigmatic disease by summarizing the current knowledge on CUPs focusing on recent discoveries and emerging diagnostic strategies.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Immunohistochemical Biomarkers of Gastrointestinal, Pancreatic, Pulmonary, and Thymic Neuroendocrine Neoplasms

Neuroendocrine neoplasms (NENs) are a heterogeneous group of epithelial neoplastic proliferations that irrespective of their primary site share features of neural and endocrine differentiation including the presence of secretory granules, synaptic-like vesicles, and the ability to produce amine and/or peptide hormones. NENs encompass a wide spectrum of neoplasms ranging from well-differentiated indolent tumors to highly aggressive poorly differentiated neuroendocrine carcinomas. Most cases arise in the digestive system and in thoracic organs, i.e., the lung and thymus. A correct diagnostic approach is crucial for the management of patients with both digestive and thoracic NENs, because their high clinical and biological heterogeneity is related to their prognosis and response to therapy. In this context, immunohistochemistry represents an indispensable diagnostic tool that pathologists need to use for the correct diagnosis and classification of such neoplasms. In addition, immunohistochemistry is also useful in identifying prognostic and theranostic markers. In the present article, the authors will review the role of immunohistochemistry in the routine workup of digestive and thoracic NENs.

NKX2.2, PDX-1 and CDX-2 as potential biomarkers to differentiate well-differentiated neuroendocrine tumors

Background

Well-differentiated neuroendocrine tumors (NET) most frequently arise from the gastrointestinal tract (GI), pancreas, and lung. Patients often present as metastasis with an unknown primary, and the clinical management and outcome depend on multiple factors, including the accurate diagnosis with the tumor primary site. Determining the site of the NET with unknown primary remains challenging. Many biomarkers have been investigated in primary NETs and metastatic NETs, with heterogeneous sensitivity and specificity observed.

Methods

We used high-throughput tissue microarray (TMA) and immunohistochemistry (IHC) with antibodies against a panel of transcriptional factors including NKX2.2, PDX-1, PTF1A, and CDX-2 on archived formalin-fixed paraffin-embedded NETs, and investigated the protein expression pattern of these transcription factors in 109 primary GI (N = 81), pancreatic (N = 17), and lung (N = 11) NETs.

Results

Differential expression pattern of these markers was observed. In the GI and pancreatic NETs (N = 98), NKX2.2, PDX-1, and CDX-2 were immunoreactive in 82 (84%), 14 (14%), and 52 (52%) cases, respectively. PDX-1 was expressed mainly in the small intestinal and appendiceal NETs, occasionally in the pancreatic NETs, and not in the colorectal NETs. All three biomarkers including NKX2.2, PDX-1, and CDX-2 were completely negative in lung NETs. PTF1A was expressed in all normal and neuroendocrine tumor cells.

Conclusions

Our findings suggest that NKX2.2 was a sensitive and specific biomarker for the GI and pancreatic neuroendocrine tumors. We proposed that a panel of immunostains including NKX2.2, PDX-1, and CDX-2 may show diagnostic utility for the most common NETs.

Pathology of Neuroendocrine Tumours of the Female Genital Tract

Neuroendocrine tumours are uncommon or rare at all sites in the female genital tract. The 2014 World Health Organisation (WHO) Classification of neuroendocrine tumours of the endometrium, cervix, vagina and vulva has been updated with adoption of the terms low-grade neuroendocrine tumour and high-grade neuroendocrine carcinoma. In the endometrium and cervix, high-grade neoplasms are much more prevalent than low-grade and are more common in the cervix than the corpus. In the ovary, low-grade tumours are more common than high-grade carcinomas and the term carcinoid tumour is still used in WHO 2014. The term ovarian small-cell carcinoma of pulmonary type is included in WHO 2014 for a tumour which in other organs is termed high small-cell neuroendocrine carcinoma. Neuroendocrine tumours at various sites within the female genital tract often occur in association with other neoplasms and more uncommonly in pure form.

Gastric Cancer Metastatic to the Pituitary Gland: A Case Report

Neoplasms from almost every tissue have been reported to metastasize to the pituitary. Gastric carcinoma is a rare cause of metastases in pituitary gland. Gastric carcinoma will be the primary tumor in less than 2% of patients with pituitary gland metastases. We report the case of a 60-years old white man with liver metastasis from gastric cancer with fair presentation symptoms of pituitary gland metastasis. Basal endocrinological work-up showed corticotroph, gonadotroph, somatotroph and thyrotroph cell insufficiency; serum PRL was elevated and no deficit of the ADH level was observed. Despite the hormonal deficits the patient did not report any specific symptom. After diagnosis the patient began thyroid and adrenal-replacement therapy and was referred to Radiotherapy Unit for treatment on the sellar and pituitary gland region.

Immunohistochemistry, carcinomas of unknown primary, and incidence rates

Pathologists use immunohistochemistry is their day-to-day practices to assist in distinguishing site of origin of metastatic carcinomas. Here, the work-up is discussed neuroendocrine carcinomas, squamous cell carcinomas and adenocarcinomas with particular attention to tumor incident rates and predictive values of the best-performing immunohistochemical markers.

Aberrant CDX2 expression in hepatocellular carcinomas: an important diagnostic pitfall

CDX2 is a sensitive and specific marker of intestinal differentiation. It is routinely used in surgical pathology, as its expression within a tumor favors an origin within the gastrointestinal tract. We had anecdotally encountered occasional hepatocellular carcinomas (HCCs) that were CDX2 positive. CDX2 expression in HCC has not yet been reported, but it has also not been examined in detail. Therefore, we evaluated CDX2 expression in a large number of resected HCCs. Full tumor sections from 172 resected HCCs and 6 resected fibrolamellar carcinomas (FLCs) were stained for CDX2. Nine (5.2%) of 172 HCCs were positive for CDX2, whereas all 6 FLCs were negative. CDX2 expression in HCCs was more commonly seen in poorly differentiated tumors (5 of 16 cases, 31%) than well and moderately differentiated tumors (4 of 156 cases, 2.5%), P = .0004. No other statistically significant correlations were observed (P>.05). Results of our study show that a small subset (5%) of HCCs can be CDX2 positive. Awareness of this phenomenon is important because CDX2 expression in a liver tumor does not completely exclude a diagnosis of HCC.

Practical Applications in Immunohistochemistry: Carcinomas of Unknown Primary Site

CONTEXT

-Identification of the site of origin of carcinoma of unknown primary using immunohistochemistry is a frequent requirement of anatomic pathologists. Diagnostic accuracy is crucial, particularly in the current era of targeted therapies and smaller sample sizes.

OBJECTIVES

-To provide practical guidance and suggestions for classifying carcinoma of unknown primary using both proven and new antibodies, as well as targeting panels based on integration of morphologic and clinical features.

DATA SOURCES

-Literature review, the authors' practice experience, and authors' research.

CONCLUSIONS

-With well-performed and interpreted immunohistochemistry panels, anatomic pathologists can successfully identify the site of origin of carcinoma of unknown primary. It is crucial to understand not only the diagnostic uses of the many available antibodies but also the potential limits and pitfalls.

Problems with the diagnosis of metastatic neuroendocrine neoplasms. Which diagnostic criteria should we use to determine tumor origin and help guide therapy?

Neuroendocrine neoplasms (NENs) can often present with metastatic disease before the primary tumor is discovered. Metastatic lesions are generally classified as well differentiated and poorly differentiated for prognostic and therapeutic purposes. In addition, for well-differentiated neuroendocrine tumors (WDNETs), pathologists are expected to determine the site of origin, if not already known, and grade the tumors. However, it is often difficult for pathologists to provide this information with certainty without knowing the site of tumor origin, as different criteria have been proposed by WHO for classification of gastrointestinal and pulmonary NENs. In this review, we will discuss the current classification and grading schema of NENs and their impact on clinical care, the differential diagnosis of NENs, the use of immunohistochemical stains that help identify tumor site of origin, and a proposed approach for the diagnosis and classification of metastatic NENs.

High-grade poorly differentiated neuroendocrine carcinomas of the gastroenteropancreatic system: from morphology to proliferation and back

Poorly differentiated neuroendocrine carcinomas (PDNECs) of the gastroenteropancreatic system (GEP) are a heterogeneous group of aggressive malignancies with a high propensity for distant metastases and an ominous prognosis. They have traditionally been divided into small and large cell subtypes on morphological grounds. However, histological diagnosis needs to be supported by immunohistochemistry to avoid possible misdiagnoses either with the more frequent poorly differentiated adenocarcinomas and squamous cell carcinomas or with lymphomas and mesenchymal neoplasms. Although it is well known that GEP PDNECs are associated with a poor prognosis, data from some published studies seem to suggest that there is a fraction of patients with PDNECs who have better survival than expected. GEP PDNECs are currently classified according to the criteria proposed in the 2010 WHO classification. They are simply called neuroendocrine carcinomas (NECs) and are defined by mitotic count >20 × 10 HPF and/or Ki-67 labeling index >20 %. However, a few recent papers have indicated that some NECs, as defined by the 2010 WHO scheme, do not show a poorly differentiated morphology as expected. This category seems to show a better prognosis and, especially, does not respond to cisplatin-based chemotherapy, which represents the goal standard therapeutic approach to high-grade PDNECs. In the present review, the main morphological, immunohistochemical, and prognostic features will be discussed as well as the opportunity to introduce a new category characterized by well to moderately differentiated morphology associated with high proliferation (mitotic count >20 × 10 HPF and/or Ki-67 index >20 %).

Use of immunohistochemistry in the diagnosis of miscellaneous and metastatic tumors of the uterine corpus and cervix

Uncommon tumors in the uterus present diagnostic challenges. In some cases, the tumor subtype is usually seen outside the gynecologic tract and the possibility of a uterine primary is not considered. In other cases, histologic overlap with more common uterine tumors leads to potential misdiagnosis. Finally, metastatic carcinoma may involve the uterus and cervix. Rarely, symptoms related to the uterine metastasis may precede diagnosis of an extrauterine primary. Without the proper clinical context, the possibility of a missed diagnosis is increased. One must first be aware of these possibilities, but immunoperoxidase studies are often necessary to confirm the diagnosis. In this review, unusual and metastatic tumors involving the uterine corpus and cervix and immunoperoxidase studies used to diagnosis such tumors are discussed.

The immunohistochemical expression of islet 1 and PAX8 by rectal neuroendocrine tumors should be taken into account in the differential diagnosis of metastatic neuroendocrine tumors of unknown primary origin

Rectal neuroendocrine tumors (NETs) can be classified by histologic pattern and secretory products. Recently, rectal NETs have been noted to exhibit immunohistochemical (IHC) positivity for Islet 1 and PAX8, which are generally considered markers for NETs of pancreatic origin. In this study, we sought to characterize the IHC staining profile of rectal NETs and determine whether there was any correlation between the histologic pattern of rectal NETs and their IHC profile. Fifty-six primary rectal NETs were histologically reviewed and stained with antibodies against Islet 1, PAX8, CDX2, chromogranin A, and synaptophysin. In a subset of 31 cases, immunoreactivity for serotonin, pancreatic polypeptide (PP), and prostatic acid phosphatase (PAP) was also studied. By morphology, the tumors studied included 55 % trabecular, 27 % solid nested, 4 % acinar, and 14 % mixed patterns. Islet 1 was positive in 89 % and PAX8 in 79 % of cases. CDX2 was negative in all 56 cases. Cytoplasmic staining was observed for chromogranin A in 30 % of cases and for synaptophysin in all 56 cases. Cytoplasmic staining for serotonin, PP, and PAP was present in 16, 61, and 97 % of cases, respectively. There was no correlation between histologic pattern and IHC staining pattern with any of the antibodies studied. We have demonstrated that Islet 1 and PAX8 are not entirely specific for NETs of pancreatic origin, as they are expressed in a majority of rectal NETs. Since rectal NETs may show an IHC staining profile which mirrors that of pancreatic NETs (Islet 1 and PAX8-positive, CDX2-negative), a metastatic rectal NET should be considered in the differential diagnosis and ruled out clinically in the work-up of a metastatic NET of unknown primary origin which exhibits this staining profile.

IMP3, NESP55, TTF-1 and CDX2 serve as an immunohistochemical panel in the distinction among small-cell carcinoma, gastrointestinal carcinoid, and pancreatic endocrine tumor metastasized to the liver

Histopathologic distinction among small-cell carcinoma (SCC), pancreatic endocrine tumor (PET), and gastrointestinal carcinoids metastasized to the liver in needle core biopsies can be extremely challenging because of limited material, crush artifact, and lack of detailed clinical history. In this study, a total of 61 surgically resected or biopsied specimens, including 27 SCCs (lung, 17; colon, 1; gallbladder, 2; stomach, 1; and unknown primary, 6), 18 gastrointestinal carcinoid tumors (GICTs) (stomach, 2; small intestine, 14; colon, 2), and 16 PETs were immunohistochemically examined for the expression of IMP3, TTF-1, CDX2, and NESP55 to evaluate their diagnostic value. The results showed that 24 (89%) of 27 SCCs exhibited strong cytoplasmic staining for IMP3 in 60% to 100% of the tumor cells. Eighteen (67%) SCCs were strongly and diffusely positive for TTF-1. In the remaining 9 TTF-1-negative SCCs (including 4 extrapulmonary cases), 7 showed strong and diffuse IMP3 expression. All SCCs were negative for CDX2 except for 1 case of colonic origin that showed strong CDX2 immunoreactivity. All 16 metastatic PETs were positively stained for IMP3 with 12 cases (75%) showing a diffuse and moderate-to-strong staining pattern while they were negative for TTF-1. Six PETs exhibited moderate-to-strong positivity for CDX2 with nuclear staining in 5% to 40% of tumor cells, and 5 showed a varying degree of positivity for NESP55. Three (17%) of 18 metastatic GICTs showed moderate IMP3 staining in 50% to 90% of the tumor cells, whereas CDX2 was expressed in 17 (94%) cases with moderate-to-strong staining in 50% to 100% of tumor cells. No NESP55 immunoreactivity was detected in metastatic SCCs and GICTs. In conclusion, a panel of these 4 markers is useful in segregating among SCC, PET, and GICT to help determine the primary site of hepatic metastasis.

Demonstration of CDX2 is highly antibody dependant

OBJECTS

CDX2 is a widely used immunohistochemical marker for intestinal differentiation in neoplasms. In the Nordic Immunohistochemical Quality Control external quality assessment scheme, only 45% of the laboratories participating in the CDX2 challenge in 2009 produced sufficient staining. A major cause of insufficient staining results appeared to be less successful primary antibody (Ab) clones. To evaluate the Ab performance in a standardized way, a comparative study was carried out.

MATERIALS AND METHODS

Tissue microarrays containing 309 non-neoplastic tissues and tumor samples with expected high, low, and no CDX2 expression were used. Five Abs were selected for comparison: EPR2764Y concentrated (Conc), EPR2764Y in a ready-to-use format, and DAK-CDX2, AMT28, and CDX2-88, all Conc. The CDX2 stains were scored blindly using the H-score method. Tissue/tumor samples with a maximum H-score of 150 to 300 (on the basis of the staining giving the highest score) were classified as CDX2 high expressors, samples with a maximum H-score of 10 to 149 as low expressors, and samples with a maximum H-score <10 as negative.

RESULTS AND CONCLUSIONS

A total of 106 tumors were CDX2 positive with at least one of the Abs. For 56 high-expressor tumors, the mean H-scores with EPR2764Y Conc, EPR2764Y ready-to-use, DAK-CDX2, AMT28, and CDX2-88 were 262, 236, 234, 167, and 149, respectively, and the percentage of positive tumors 100, 100, 100, 98, and 93, respectively. For 50 low-expressor tumors, the mean H-scores with the same Abs were 59, 26, 28, 7, and 5, respectively, and the percentage of positive tumors 98, 58, 64, 18, and 14, respectively. With EPR2764Y Conc, CDX2 was demonstrated in 5/19 (26%) urothelial carcinomas, 7/64 (11%) lung adenocarcinomas, 5/30 (17%) large cell/sarcomatoid lung carcinomas, and 4/19 (21%) esophagus squamous cell carcinomas. In-house optimized protocols gave for all 4 Conc Abs better staining results than the vendors' recommended protocols. The sensitivity of CDX2 Abs and protocols must be taken into consideration when classifying neoplasms of unknown origin.

Islet-1 is a sensitive but not entirely specific marker for pancreatic neuroendocrine neoplasms and their metastases

Islet-1 (Isl1) is a transcription factor involved in the embryogenesis of islets of Langerhans. Immunohistochemically, Isl1 is a sensitive lineage-specific marker for pancreatic neuroendocrine neoplasms (NENs) and their metastases. Its specificity has not been documented, nor have large numbers of NENs from other parts of the gut or other organs been studied. We examined Isl1 expression in 203 primary NENs (gastroenteropancreatic, lung, breast, and ovarian neoplasms) and 40 hepatic NEN metastases (enteropancreatic and lung neoplasms) from known primaries. The correlation between Isl1 and CDX2 expression was studied using a tissue microarray containing 46 pancreatic NENs. Immunostaining for Isl1 and CDX2 was also performed in selected NENs from other sites. Isl1 was positive in 90% of pancreatic, 89% of duodenal, 100% of rectal, 38% of colonic, 14% of appendiceal, and 6% of ileal primaries. Isl1 was negative in all other NENs. Among metastatic neoplasms, 76% of pancreatic and 2 of 2 rectal NEN metastases were Isl1 positive, whereas all other tested metastases were negative. The overall sensitivity and specificity of Isl1 in identifying primary pancreatic NENs was 88% and 80%, respectively. Thirty-six of 46 pancreatic NENs in the tissue microarray were Isl1 positive; 4 were Isl1 negative but CDX2 positive. Our findings confirm that Isl1 is a sensitive marker of pancreatic origin in cases of metastatic NEN. However, Isl1 does not distinguish pancreatic NEN from duodenal and colorectal NEN, even when used in association with CDX2.

Achaete-scute homolog 1 as a marker of poorly differentiated neuroendocrine carcinomas of different sites: a validation study using immunohistochemistry and quantitative real-time polymerase chain reaction on 335 cases

Neuroendocrine carcinomas show overlapping morphological and immunohistochemical features independently of their site of origin, which makes identification of the primary location problematic when they are diagnosed as metastases of unknown origin. Neuroendocrine carcinomas are easily morphologically differentiated from neuroendocrine tumors in surgical material, although this distinction can be difficult when using small biopsy specimens. The diagnostic usefulness of different transcription factors as site-specific markers or as discriminating markers between neuroendocrine carcinomas and neuroendocrine tumors has been previously studied with sometimes contradictory results. In this respect, the role of achaete-scute homolog 1 has been poorly investigated, although some recent findings demonstrate its expression in neuroendocrine carcinomas. Using immunohistochemistry and quantitative real-time polymerase chain reaction, we investigated the expression of achaete-scute homolog 1 in 335 neuroendocrine neoplasms (194 neuroendocrine carcinomas and 141 neuroendocrine tumors) of different sites, to check its possible utility as diagnostic marker. High concordance between immunohistochemical and molecular findings was found. Achaete-scute homolog 1 expression was identified in 82% of lung neuroendocrine carcinomas and 70% of extrapulmonary neuroendocrine carcinomas. Achaete-scute homolog 1 was not detected in any gastroenteropancreatic neuroendocrine tumor and was found in only a minority of lung carcinoids. The diagnostic sensitivity and specificity of achaete-scute homolog 1 expression were 82.4% and 89.7% in distinguishing neuroendocrine carcinomas from neuroendocrine tumors of the lung, 40.6% and 100% to differentiate extrapulmonary neuroendocrine carcinomas from neuroendocrine tumors, and 82.4% and 59.4% in distinguishing lung from extrapulmonary neuroendocrine carcinomas. Our data suggest that achaete-scute homolog 1 is not a site-specific marker. However, achaete-scute homolog 1 may be proposed as a diagnostic marker of poor differentiation and may help to differentiate neuroendocrine carcinomas from neuroendocrine tumors in difficult cases.

Value of thyroid transcription factor-1 immunostaining in tumor diagnosis: a review and update

Thyroid transcription factor-1 (TTF-1) is a tissue-specific transcription factor that plays a critical role in the normal development of embryonic epithelial cells of the thyroid and lung. Because TTF-1 expression is highly restricted to epithelial tumors arising in these organs, it is, at present, one of the immunohistochemical markers most commonly used to assist in the differential diagnosis of carcinomas of the lung and thyroid. Recent studies, however, have reported that TTF-1 is not as specific for lung and thyroid carcinomas as was previously thought as it can be found to be expressed, although much less frequently, in some carcinomas arising in other organs, such as the ovaries, endometrium, colon, and breast, as well as in some tumors of the central nervous system. Even though this unexpected TTF-1 positivity has been reported more frequently with the recently available SPT24 anti-TTF-1 monoclonal antibody, it has also been shown to occur with the commonly used 8G7G3/1 clone, albeit in a lower percentage of cases. Despite these findings, TTF-1 remains a very useful immunohistochemical marker in diagnostic pathology.

Immunohistochemical features of the gastrointestinal tract tumors

Gastrointestinal tract tumors include a wide variety of vastly different tumors and on a whole are one of the most common malignancies in western countries. These tumors often present at late stages as distant metastases which are then biopsied and may be difficult to differentiate without the aid of immunohistochemical stains. With the exception of pancreatic and biliary tumors where there are no distinct immunohistochemical patterns, most gastrointestinal tumors can be differentiated by their unique immunohistochemical profile. As the size of biopsies decrease, the role of immunohistochemical stains will become even more important in determining the origin and differentiation of gastrointestinal tract tumors.

PDX-1, CDX-2, TTF-1, and CK7: a reliable immunohistochemical panel for pancreatic neuroendocrine neoplasms

Neuroendocrine tumors (NETs) occur in virtually all sites of the body. As NETs arising in different organs share similar morphologic features, distinguishing metastatic from primary NETs on the basis of morphologic grounds alone is difficult. Pancreatic duodenal homeobox 1 (PDX-1) is a Hox-type transcription factor that is essential for both exocrine and endocrine pancreatic differentiation and maintenance of β-cell function. We investigated PDX-1 as an immunohistochemical (IHC) marker in primary pancreatic NETs. Eighty primary NETs [25 pancreatic, 29 bronchopulmonary, and 26 in the gastrointestinal (GI) tract] and 13 metastatic NETs in the liver were studied. Clinical and radiologic data were reviewed to confirm the stated primary sites. IHC analysis for PDX-1, CDX-2, thyroid transcription factor-1 (TTF-1), keratin 7 (CK7), and keratin 20 (CK20) was performed, and the results were based on review blinded to the primary sites. PDX-1 was seen in 18 of 25 (72%) pancreatic NETs; in contrast, only 3 of 29 (10%) bronchopulmonary NETs and 1 of 26 (4%) GI NETs were positive. PDX-1 was therefore 93% specific and 72% sensitive for pancreatic NETs. TTF-1 was expressed only in bronchopulmonary NETs; all other NETs were negative for TTF-1. CK7 was also very specific (92%) and moderately sensitive (66%) for bronchopulmonary NETs. CDX-2 was seen in 22 of 26 (85%) cases of GI NETs and in only 1 of 51 (2%) cases of extra-GI NETs. Thus, CDX-2 was 98% specific and 85% sensitive for GI NETs. In terms of metastatic NETs found in the liver, PDX-1 was positive in 5 of 5 cases of metastatic pancreatic NETs and 2 of 2 cases of metastatic duodenal NETs. PDX-1 is highly specific, with very good overall diagnostic accuracy for pancreatic NETs. An IHC panel including PDX-1, CDX-2, TTF-1, CK7, and CK20 may be useful in distinguishing NETs of pancreatic origin from other primaries.

Value of Islet 1 and PAX8 in identifying metastatic neuroendocrine tumors of pancreatic origin

Neuroendocrine tumors can present as liver metastases before discovery of the primary tumor. Islet 1 and PAX8 have recently been proposed as markers for neuroendocrine tumors of pancreatic origin. In this study, we compared the utility of Islet 1 and PAX8 in distinguishing pancreatic neuroendocrine tumors from neuroendocrine tumors of other sites and determined the usefulness of an immunohistochemical panel, including TTF1, CDX2, Islet 1 and/or PAX8, in identifying metastatic pancreatic neuroendocrine tumors. A total of 110 primary neuroendocrine tumors (33 pancreatic, 31 pulmonary, 23 ileal, 14 rectal, and 9 gastric) and 73 metastatic neuroendocrine tumors (28 pancreatic, 5 pulmonary, 37 ileal, 1 rectal, 1 colonic, and 1 duodenal) were studied. Islet 1 and PAX8 were positive in 27/33 (82%) and 29/33 (88%), respectively, of primary pancreatic neuroendocrine tumors, and in 19/28 (68%) and 15/28 (54%), respectively, of metastatic pancreatic neuroendocrine tumors. No cases of primary (0/23) or metastatic (0/37) ileal neuroendocrine tumors were positive with either Islet 1 or PAX8. There was Islet 1 positivity in 2/31 (6%) primary pulmonary, 12/14 (86%) primary rectal, and 1/1 metastatic rectal neuroendocrine tumors, and PAX8 positivity in 7/31 (23%) primary pulmonary, 11/14 (79%) primary rectal, and 2/9 (22%) primary gastric neuroendocrine tumors. ROC curve analysis incorporating sensitivity and specificity data of immunohistochemical panels for metastatic pancreatic neuroendocrine tumors showed that a four-stain panel, including Islet 1, PAX8, TTF1, and CDX2 significantly outperformed a three-stain panel composed of PAX8, TTF1, and CDX2 (P=0.019), and also showed a trend for better performance compared with a three-stain panel composed of Islet 1, TTF1, and CDX2 (P=0.072). Both Islet 1 and PAX8 are reliable immunohistochemical markers for pancreatic neuroendocrine tumors and would be useful adjuncts to other markers (TTF1, CDX2) currently used to work up a metastatic neuroendocrine tumor of unknown primary.

Colorectal poorly differentiated neuroendocrine carcinomas and mixed adenoneuroendocrine carcinomas: insights into the diagnostic immunophenotype, assessment of methylation profile, and search for prognostic markers

Colorectal poorly differentiated neuroendocrine carcinomas (NECs) and mixed adenoneuroendocrine carcinomas (MANECs) are well-recognized entities generally known to be associated with biological aggressiveness and poor patient survival. However, a few published papers have highlighted the existence of a subgroup of tumors with a better survival than expected; however, to date, there are no established parameters that usefully identify this category. In the present study we have investigated the morphologic features, the CpG methylator phenotype (CIMP), microsatellite instability (MSI), and the immunohistochemical profile, including the expression of transcription factors (TTF1, ASH1, CDX2, and PAX5), stem cell markers (CD117 and CD34), and cytokeratins 7 and 20, in a series of 39 carcinomas (27 NECs and 12 MANECs) to better characterize such neoplasms and to search for prognostic indicators. No different patient survival was observed between NECs and MANECs. Neoplasms showed a heterogenous spectrum of morphologic and immunohistochemical features; however, only large-cell subtype, significant peritumoral lymphoid reaction, CD117 immunoreactivity, vascular invasion, and MSI/CIMP+ status were significantly correlated with prognosis on univariable analysis. Furthermore, vascular invasion and CD117 immunoreactivity were independent prognostic markers on multivariable analysis. In addition to these prognostic features, neoplasms showed different expression of transcription factors, stem cell markers, and cytokeratins that should be considered for diagnostic purposes and, especially, for discriminating among possible differential diagnoses.

[Neuroendocrine neoplasms of the gastrointestinal tract. Classification, clinical presentation and diagnosis]

Neuroendocrine neoplasms of the digestive system represent a rare and heterogeneous group of malignancies with various clinical presentations and prognoses. The WHO classification for the year 2000 was updated in 2010 to take the histopathology and tumor biology of these tumors into account. Together with proliferation-based grading and the recently established staging system using the ENETS TNM classification, it forms the basis for the further diagnostic and therapeutic approach. Clinical presentation depends mainly on the primary site of the tumor and its functionality. Characteristic symptoms are seen only rarely, this being the reason these tumors are usually detected at an advanced stage. Approximately 30% of GEP-NEN are hormonally active and can cause a specific clinical syndrome. In addition to these specific hormones, chromogranin A is considered the most accurate general marker for the biochemical follow-up of these patients. In addition to commonly used radiological and endoscopic imaging modalities, somatostatin receptor-based functional imaging using either octreotide scintigraphy or novel PET-based techniques with specific isotopes such as Ga68-DOTA-octreotate play a crucial role in the detection of the primary tumor as well as in the evaluation of tumor extent and the selection of patients for receptor-based radionuclide therapy.

MicroRNAs-based network: a novel therapeutic agent in pituitary adenoma

Pituitary adenomas are common benign intracranial neoplasms representing about 10-25% of all intracranial neoplasm. Significant morbidity can occur along with pituitary adenomas due to hormonal dysfunction and mass effects. The pathogenesis of pituitary adenoma is unclear, however, etiologic factors include genetic events, hormonal stimulation, and growth factors [1], all of which promote cell proliferation and transformation in the tumor. However, genetic events play the most important role in tumorigenesis. MicroRNAs (miRNAs), a class of non-coding RNAs, not only have function in pituitary cell proliferation and apoptosis but also in neoplastic transformation. It has been shown that miRNAs are differentially expressed in pituitary adenoma when compared with the normal pituitary gland; moreover, miRNAs have been identified as a predictive signature of pituitary adenoma and can be used to predict the histotype. The expression of miRNAs can be used not only to differentiate microadenomas from macroadenomas, but to also distinguish samples of treated patients from samples of non-treated patients. Therefore, we hypothesized that a miRNA-based network may be involved in pituitary tumorigenesis and it can potentially serve as useful diagnostic markers to improve the classification of pituitary adenomas. Here, we reviewed the therapeutic potential that different types of miRNAs may play in tumorigenesis. Moreover, miRNAs may emerge as potential therapeutic targets. We speculated the mechanism of miR-21 is involved in tumorigenesis, leading to improvements in therapies and prevention of metastasis.

The novel WHO 2010 classification for gastrointestinal neuroendocrine tumours correlates well with the metastatic potential of rectal neuroendocrine tumours

BACKGROUND

Approximately 10-15% of gastroenteropancreatic neuroendocrine tumours (NETs, carcinoids) occur in the rectum, some of which are potentially able to metastasize. The new WHO 2010 classification of NETs applies to all gastroenteropancreatic NETs, but no reports have studied its correlation with the prognosis of rectal NETs.

PATIENTS AND METHODS

We retrospectively classified 73 rectal NETs according to the novel WHO 2010 and the previous WHO 2000 classifications. The aim was to assess the validity of the classifications in distinguishing indolent rectal NETs from metastasising tumours.

RESULTS

Using the WHO 2010 criteria, we identified 61 G1 tumours, none of which had metastasised during follow-up. Of 11 G2 tumours, 9 had shown distant metastases. The only G3 neuroendocrine carcinoma that occurred had been disseminated at initial presentation.

CONCLUSION

Our results show that rectal NETs classified as G1 according to the WHO 2010 classification have an indolent clinical course, whereas G2 NETs often metastasise. The WHO 2010 classification of NETs predicts the metastatic potential of rectal NETs better than the WHO 2000 classification.

Heterogeneity of large cell carcinoma of the lung: an immunophenotypic and miRNA-based analysis

Large cell carcinomas (LCCs) of the lung are heterogeneous and may be of different cell lineages. We analyzed 56 surgically resected lung tumors classified as LCC on the basis of pure morphologic grounds, using a panel of immunophenotypic markers (adenocarcinoma [ADC]-specific, thyroid transcription factor-1, cytokeratin 7, and napsin A; squamous cell carcinoma [SQCC]-specific, p63, cytokeratin 5, desmocollin 3, and Δnp63) and the quantitative analysis of microRNA-205 (microRNA sample score [mRSS]). Based on immunoprofiles 19 (34%) of the cases were reclassified as ADC and 14 (25%) as SQCC; 23 (41%) of the cases were unclassifiable. Of these 23 cases, 18 were classified as ADC and 5 as SQCC according to the mRSS. Our data show that an extended panel of immunohistochemical markers can reclassify around 60% of LCCs as ADC or SQCC. However, a relevant percentage of LCCs may escape convincing immunohistochemical classification, and mRSS could be used for further typing, but its clinical relevance needs further confirmation.

Hormonally defined pancreatic and duodenal neuroendocrine tumors differ in their transcription factor signatures: expression of ISL1, PDX1, NGN3, and CDX2

We recently identified the transcription factor (TF) islet 1 gene product (ISL1) as a marker for well-differentiated pancreatic neuroendocrine tumors (P-NETs). In order to better understand the expression of the four TFs, ISL1, pancreatico-duodenal homeobox 1 gene product (PDX1), neurogenin 3 gene product (NGN3), and CDX-2 homeobox gene product (CDX2), that mainly govern the development and differentiation of the pancreas and duodenum, we studied their expression in hormonally defined P-NETs and duodenal (D-) NETs. Thirty-six P-NETs and 14 D-NETs were immunostained with antibodies against the four pancreatic hormones, gastrin, serotonin, calcitonin, ISL1, PDX1, NGN3, and CDX2. The TF expression pattern of each case was correlated with the tumor's hormonal profile. Insulin-positive NETs expressed only ISL1 (10/10) and PDX1 (9/10). Glucagon-positive tumors expressed ISL1 (7/7) and were almost negative for the other TFs. Gastrin-positive NETs, whether of duodenal or pancreatic origin, frequently expressed PDX1 (17/18), ISL1 (14/18), and NGN3 (14/18). CDX2 was mainly found in the gastrin-positive P-NETs (5/8) and rarely in the D-NETs (1/10). Somatostatin-positive NETs, whether duodenal or pancreatic in origin, expressed ISL1 (9/9), PDX1 (3/9), and NGN3 (3/9). The remaining tumors showed labeling for ISL1 in addition to NGN3. There was no association between a particular TF pattern and NET features such as grade, size, location, presence of metastases, and functional activity. We conclude from our data that there is a correlation between TF expression patterns and certain hormonally defined P-NET and D-NET types, suggesting that most of the tumor types originate from embryologically determined precursor cells. The observed TF signatures do not allow us to distinguish P-NETs from D-NETs.

PAX8 expression reliably distinguishes pancreatic well-differentiated neuroendocrine tumors from ileal and pulmonary well-differentiated neuroendocrine tumors and pancreatic acinar cell carcinoma

PAX (paired box) genes encode a family of transcription factors that regulate organogenesis in a variety of organs. Very little is known about the role of PAX8 in endocrine cell development and the expression of PAX8 in neuroendocrine tumors. The purpose of this study was to analyze PAX8 immunohistochemical expression in gastroenteropancreatic and pulmonary well-differentiated neuroendocrine tumors to determine whether PAX8 can reliably distinguish pancreatic neuroendocrine tumors from neuroendocrine tumors of other anatomic sites and other pancreatic non-ductal neoplasms. In total, 221 well-differentiated neuroendocrine tumors were evaluated: 174 primary neuroendocrine tumors (66 pancreatic, 31 ileal, 21 pulmonary, 20 gastric, 17 rectal, 11 appendiceal, and 8 duodenal) and 47 neuroendocrine tumors metastatic to the liver (31 pancreatic, 11 ileal, 2 pulmonary, 2 duodenal, and 1 rectal). Fifteen solid-pseudopapillary neoplasms and six acinar cell carcinomas of the pancreas were also evaluated. PAX8 was positive in 49/66 (74%) primary pancreatic neuroendocrine tumors. PAX8 expression did not correlate with World Health Organization categorization, grade, size, functional status, or the presence of liver or lymph node metastasis. PAX8 expression was identified in 0/31 (0%) ileal, 0/21 (0%) pulmonary, 2/20 (10%) gastric, 5/17 (29%) rectal, 1/11 (9%) appendiceal, and 6/8 (75%) duodenal neuroendocrine tumors. PAX8 was positive in 4/15 (27%) solid-pseudopapillary neoplasms of the pancreas, whereas all acinar cell carcinomas (0/6) lacked immunoreactivity. Among liver metastases, only pancreatic neuroendocrine tumors (20/31, 65%) were PAX8 positive, whereas no cases of ileal (0/11), pulmonary (0/2), duodenal (0/2), and rectal (0/1) neuroendocrine tumor metastases were PAX8 positive. PAX8 is expressed in primary and metastatic pancreatic well-differentiated neuroendocrine tumors, and its expression can reliably distinguish pancreatic from ileal and pulmonary well-differentiated neuroendocrine tumors. Duodenal neuroendocrine tumors and a subset of rectal, gastric, and appendiceal neuroendocrine tumors may also express PAX8. PAX8 expression can distinguish pancreatic neuroendocrine tumors from acinar cell carcinomas, but its utility in distinguishing neuroendocrine tumors from solid-pseudopapillary neoplasms is limited.

PAX8 is expressed in pancreatic well-differentiated neuroendocrine tumors and in extrapancreatic poorly differentiated neuroendocrine carcinomas in fine-needle aspiration biopsy specimens

BACKGROUND

PAX (paired box) genes encode a family of transcription factors important for organogenesis. Recently, PAX8 has been recognized as a potential immunohistochemical marker of pancreatic neuroendocrine tumors. The authors evaluated PAX8 expression in fine-needle aspiration biopsies of neuroendocrine tumors to establish whether PAX8 immunohistochemistry can be used as an ancillary marker of pancreatic origin for neuroendocrine tumors.

METHODS

Fine-needle aspiration biopsies from 72 neuroendocrine tumors were evaluated for PAX8 expression: 32 primary and 23 metastatic well-differentiated neuroendocrine tumors (25 pancreatic, 13 pulmonary, 3 ileal, 2 duodenal, 1 rectal, 1 ovarian, and 10 primary site unknown) and 17 poorly differentiated neuroendocrine carcinomas (11 pulmonary, 1 pancreas, 1 breast, 1 thymus, and 3 primary site unknown).

RESULTS

Among well-differentiated neuroendocrine tumors, only tumors from the pancreas were PAX8 positive (14 of 25, 56%) whereas no cases of pulmonary (0 of 13), ileal (0 of 3), duodenal (0 of 2), rectal (0 of 1), or ovarian (0 of 1) well-differentiated neuroendocrine tumors were positive for PAX8. One of 10 (10%) well-differentiated neuroendocrine tumors of unknown primary origin was PAX8 positive. Among poorly differentiated neuroendocrine carcinomas, PAX8 expression was identified in 1 of 1 (100%) pancreatic, 1 of 1 (100%) thymic, 4 of 11 (36%) pulmonary, and 0 of 1 (0%) breast carcinomas. One of 3 (33%) poorly differentiated neuroendocrine carcinomas of unknown primary origin was PAX8 positive.

CONCLUSIONS

Pancreatic well-differentiated neuroendocrine tumors frequently express PAX8, which can help distinguish pancreatic primary tumors from tumors of other anatomic sites. In contrast, PAX8 expression in poorly differentiated neuroendocrine carcinomas is not specific for pancreatic origin and can be seen in extrapancreatic poorly differentiated neuroendocrine carcinomas.

Diagnostic approach to pancreatic tumors with the specimens of endoscopic ultrasound-guided fine needle aspiration

Endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) has enabled clinicians to histologically diagnose pancreatic tumors. However, EUS-FNA specimens often result in tiny fragmented tissues, so auxiliary utilities are necessary. Using immunostaining of CK7, CDX2, neuroendocrine markers and KRAS mutation analysis, we examined 57 FNA cell block sections and 61 surgically-resected specimens (25 invasive ductal carcinomas, 25 endocrine tumors, and 11 acinar cell tumors). In the majority of the matched pairs, the diagnoses between EUS-FNA and surgical specimens were concordant using the following criteria: neuroendocrine markers negative, CK7 positive, and mutated KRAS gene for invasive ductal carcinomas; neuroendocrine markers diffusely positive, CK7 and CDX2 negative, and wild-type KRAS gene for well-differentiated endocrine tumors; and neuroendocrine markers no more than focal positive, CK7 and CDX2 with various staining patterns, and wild-type KRAS gene for acinar cell carcinomas. Expression of CK7 and/or CDX2 in addition to KRAS mutations were occasionally seen in endocrine carcinomas, but not in well-differentiated endocrine tumors, suggesting that ductal differentiation in an endocrine tumor may be a predictor of aggressive disease. The usefulness of these markers was confirmed using 13 additional pancreatic tumors, prospectively. Although minimal in selection, these markers are helpful in making diagnosis from EUS-FNA specimens of the major pancreatic tumors.

Pathology of Gastrointestinal Neuroendocrine Tumors: An Update

Gastrointestinal (GI) neuroendocrine tumors (NETs) are a heterogeneous group of relatively slow-growing neoplasms with marked site-specific differences in hormonal secretion and clinical behavior. Most are sporadic neoplasms, with only 5% to 10% arising in patients with hereditary disorders, most commonly in multiple endocrine neoplasia type 1. Although a uniform terminology is not universally accepted, use of the 4-category WHO classification of these tumors is becoming more widespread, and recommendations for tumor grading and staging have been recently formulated. Most GI NETs are easily recognized on routine histologic examination; rarely, a limited panel of immunohistochemical markers may be useful in establishing the diagnosis. This article describes general and site-specific features of these tumors and outlines potential pitfalls in diagnosis.

TTF1 expression in normal lung neuroendocrine cells and related tumors: immunohistochemical study comparing two different monoclonal antibodies

Thyroid transcription factor-1 (TTF1) regulates lung morphogenesis and differentiation, and its immunohistochemical expression is used for identifying lung neoplasms. The 8G7G3/1 antibody has been used in previous studies, but a different and more sensitive anti-TTF1 antibody, named SPT24, has become commercially available. Since the immunohistochemical expression of TTF1 in normal lung neuroendocrine (NE) cells has not been previously investigated and its utility in the diagnosis of lung NE tumors is a controversial issue, we studied the TTF1 expression in normal adult and fetal lungs, in 83 pulmonary NE neoplasms, in 131 non-lung NE tumors and in 36 metastases from these neoplasms using these two antibodies. A TTF1 immunoreactivity was demonstrated in normal fetal and adult NE cells when using the SPT24 clone. Conversely, using the 8G7G3/1 antibody, only rare fetal neuroendocrine cells were TTF1 positive while adult NE cells were negative. The SPT24 clone identified TTF1 expression in more carcinoids, most of them peripherally located, and poorly differentiated NE carcinomas than the 8G7G3/1 clone. Non-pulmonary well-differentiated NE tumors were negative for both antibodies. Among the 45 non-pulmonary poorly differentiated NE carcinomas 11% were positive for 8G7G3/1 and 18% for SPT24. TTF1 expression in metastases perfectly reflected that detected in the related primary tumors. Our results indicate that the SPT24 antibody is more sensitive than the 8G7G3/1 clone for labeling lung carcinoids and it appears particularly useful in detecting peripheral neoplasms. In addition, the expression of TTF1 in normal NE cells suggests a possible role for the transcription factor in their development and differentiation.

PAX8 Expression in well-differentiated pancreatic endocrine tumors: correlation with clinicopathologic features and comparison with gastrointestinal and pulmonary carcinoid tumors

PAX (paired box) genes encode a family of transcription factors that regulate organogenesis and cell-lineage specification in multiple organ systems. In the pancreas, PAX proteins play a critical role in islet cell differentiation. We recently observed that islet cells show strong, diffuse staining for PAX8 by immunohistochemistry. However, PAX8 expression has not previously been examined in pancreatic endocrine tumors (PETs). The purpose of this study was to evaluate PAX8 expression in PETs, and to correlate expression with clinical and pathologic features and behavior. PAX8 expression in other well-differentiated neuroendocrine tumors (WDNETs) was also studied. In total, 190 tumors were evaluated: 156 primary WDNETs (63 PETs, 31 ileal, 5 duodenal, 5 gastric, 19 appendiceal, 13 rectal, and 20 pulmonary carcinoid tumors) and 34 liver metastases (18 PETs and 16 ileal carcinoid tumors). PAX8 was positive in 42/63 (67%) primary PETs. Expression of PAX8 was significantly associated with WHO category 1.1 ("benign" behavior) compared with category 1.2 (uncertain behavior) or 2 (well-differentiated endocrine carcinoma) (positive in 100%, 64%, and 52% of tumors, respectively; P<0.05). PAX8-positive PETs were also significantly smaller and more often clinically functional; PAX8-negative tumors were more frequently associated with liver metastases. PAX8 expression was not associated with patient age, gender, MIB1 index, or lymph node metastases. PAX8 expression was detected in 0/20 (0%) pulmonary, 1/5 (20%) gastric, 5/5 (100%) duodenal, 0/31 (0%) ileal, 4/19 (21%) appendiceal, and 11/13 (85%) rectal carcinoid tumors. Among the liver metastases, PAX8 was positive in 9/18 (50%) metastatic PETs compared with 0/16 (0%) metastatic ileal carcinoid tumors. In summary, PAX8 is expressed in normal pancreatic islet cells and in a high proportion of primary and metastatic PETs. In the GI tract, PAX8 is positive in the majority of duodenal and rectal carcinoid tumors, and in a minor subset of appendiceal and gastric carcinoids. PAX8 expression is absent in ileal and pulmonary carcinoid tumors. PAX8 immunostaining may be helpful in determining the primary site for a WDNET metastatic to the liver, as ileal (PAX8 negative) and pancreatic (PAX8 positive) tumors most often present as a metastasis from an occult primary. PAX8 may also be a prognostic marker in PETs, as loss of expression is associated with malignant behavior.

Diagnosis of metastatic neoplasms: an immunohistochemical approach

CONTEXT

It is important to determine the type and/or site of origin of metastatic tumors for optimal clinical management.

OBJECTIVE

To summarize the use of currently available immunohistochemical markers in the evaluation of metastatic tumors.

DATA SOURCES

Review of relevant literature on immunohistochemical evaluation of tumors and the author's personal experience.

CONCLUSIONS

Immunohistochemistry is an important ancillary technique for evaluation of metastatic tumors and should be used in the context of routine morphology and clinical information. While a single marker may be used to support a known or suspected site of origin, a carefully constructed panel is strongly recommended, particularly for tumors of morphologically uncertain lineage or origin.

Immunohistochemical staining for CDX-2, PDX-1, NESP-55, and TTF-1 can help distinguish gastrointestinal carcinoid tumors from pancreatic endocrine and pulmonary carcinoid tumors

Well-differentiated neuroendocrine tumors (WDNET) of the gastrointestinal tract, pancreas, and lung are histologically similar. Thus, predicting the site of origin of a metastasis is not possible on morphologic grounds. Prior immunohistochemical studies of WDNET have yielded conflicting results, and pancreatic and duodenal homeobox factor-1 (PDX-1) has not previously been evaluated in this context. We therefore analyzed the expression of CDX-2, PDX-1, TTF-1, and neuroendocrine secretory protein-55 (NESP-55), a recently described member of the chromogranin family, in primary and metastatic WDNET. In total, 64 gastrointestinal carcinoids (5 stomach; 5 duodenum; 31 ileum; 11 appendix; and 12 rectum); 39 pancreatic endocrine tumors (PET); and 20 pulmonary carcinoid tumors were studied. PET were positive for NESP-55 (16/39) and PDX-1 (11/39); 3/31 also showed heterogeneous positivity for CDX-2. Ileal carcinoids were exclusively positive for CDX-2 (30/31) and negative for all other markers. Appendiceal carcinoids were uniformly positive for CDX-2 (11/11). All rectal carcinoids were negative for CDX-2 and TTF-1; 2/12 were positive for PDX-1, and 1/12 for NESP-55. The gastric and duodenal carcinoids were only positive for PDX-1 (7/10). TTF-1 positivity was confined to pulmonary carcinoids (7/20); 1/20 was positive for NESP-55; and all were negative for CDX-2 and PDX-1. NESP-55 and PDX-1 positivity, in the presence of negative CDX-2 and TTF-1, was 97% specific for PET. The sensitivity and specificity of CDX-2 positivity for predicting an ileal primary, when PDX-1, NESP-55, and TTF-1 were negative, was 97% and 91%, respectively. TTF-1 positivity was confined to pulmonary carcinoids in our study but was present in only about a third of cases. A panel of these 4 markers may be useful in predicting the primary site of metastatic WDNET.

Islet 1 (Isl1) expression is a reliable marker for pancreatic endocrine tumors and their metastases

BACKGROUND

Tracing the origin of a metastasis of a neuroendocrine carcinoma is a challenge. The transcription factors Cdx2 and TTF1 have been found to be helpful in identifying well-differentiated neuroendocrine tumors of gastrointestinal and pulmonary origin, respectively. So far, such a marker is lacking for pancreatic neuroendocrine tumors (PETs) and metastases thereof. Islet1 (Isl1) is a transcription factor expressed in pancreatic islet cells. The aim of this study was (1) to test the specificity and sensitivity of Isl1 as a marker of PETs, and (2) to test the specificity and sensitivity of a panel of markers, including Isl1, Cdx2, and TTF1, for the localization of the primary.

DESIGN

One hundred eighty-eight primary gastroenteropancreatic and pulmonary endocrine tumors and 49 metastases thereof were examined. Immunohistochemistry using antibodies directed against Isl1, Cdx2, and TTF1 was performed and the staining results were scored semiquantitatively.

RESULTS

Isl1 proved to be a highly specific marker for pancreatic endocrine tumors. In 84 primary PET its specificity was 78.4% (sensitivity 74.3%) and in 18 metastases of PET the specificity reached 100% (sensitivity 77.8%). Strong Cdx2 staining showed a specificity for gastrointestinal origin of 83.9% (sensitivity 82%) in primary tumors and of 100% (sensitivity 40%) in metastases. Including weakly positive tumors lead to a decreased specificity but an increased sensitivity. TTF1 expression was detected in 2 PET and 1 ileal primary tumor only and was absent in all metastases of gastroenteropancreatic endocrine tumors.

CONCLUSIONS

Isl1 is a reliable marker of pancreatic endocrine tumors and metastases thereof. It shows a comparable sensitivity and specificity as Cdx2 as a marker of ileal and appendiceal neuroendocrine tumors and their metastases. TTF1 is very rarely expressed in well-differentiated gastroentero-PETs. Therefore, the panel of Isl1, Cdx2, and TTF1 seems useful for examining metastases of well-differentiated endocrine carcinomas of unknown origin.

Diagnostic value of CDX-2 and TTF-1 expressions in separating metastatic neuroendocrine neoplasms of unknown origin

Histomorphologic features and routine endocrine immunohistochemical (IHC) markers do not differentiate neuroendocrine tumors (NETs) in relation to their location, making it difficult to establish the site of origin of a metastatic neoplasm. Site-specific markers would be useful, particularly when examining small biopsies. CDX-2 and thyroid transcription factor-1 (TTF-1) are transcription factors that have been recently proposed as IHC markers of intestinal and pulmonary adenocarcinomas, respectively. However, their expression in NETs has not been widely studied. The objective of this study is to evaluate the expression of TTF-1 and CDX-2 in NETs and their potential usefulness in distinguishing gastrointestinal and pulmonary NETs from other sites. We performed an IHC study on formalin-fixed, paraffin-embedded sections from 155 primary NETs, including 60 pulmonary, 60 gastrointestinal, 30 pancreatic, and 5 NETs from other sites. In addition, we evaluated 13 metastatic NETs, including 11 cases of gastrointestinal and 2 of pulmonary origin. In this study, CDX-2 was expressed in 28/60 (47%) of gastrointestinal NETs with the following results: 11/11 (100%) appendiceal, 12/14 (86%) small intestinal, 3/4 (75%) colonic, 2/11 (18%) rectal, and 0/20 (0%) gastric. TTF-1 was expressed in pulmonary carcinoid tumors in 13/30 (43%) and in 27/30 (90%) pulmonary small cell carcinomas. NETs of other origins (pancreas, skin, ovary, and thymus) were negative for both TTF-1 and CDX-2. Metastatic neuroendocrine neoplasms of intestinal origin were positive for CDX-2 and negative for TTF-1. In conclusion, CDX-2 expression is highly specific in identifying NETs of intestinal origin and TTF-1 expression is helpful in identifying NETs of pulmonary origin, which can be quite useful in the diagnosis of metastatic NETs of unknown origin.

European Organisation for Research and Treatment of Cancer (EORTC) Pathobiology Group standard operating procedure for the preparation of human tumour tissue extracts suited for the quantitative analysis of tissue-associated biomarkers

With the new concept of 'individualized treatment and targeted therapies', tumour tissue-associated biomarkers have been given a new role in selection of cancer patients for treatment and in cancer patient management. Tumour biomarkers can give support to cancer patient stratification and risk assessment, treatment response identification, or to identifying those patients who are expected to respond to certain anticancer drugs. As the field of tumour-associated biomarkers has expanded rapidly over the last years, it has become increasingly apparent that a strong need exists to establish guidelines on how to easily disintegrate the tumour tissue for assessment of the presence of tumour tissue-associated biomarkers. Several mechanical tissue (cell) disruption techniques exist, ranging from bead mill homogenisation and freeze-fracturing through to blade or pestle-type homogenisation, to grinding and ultrasonics. Still, only a few directives have been given on how fresh-frozen tumour tissues should be processed for the extraction and determination of tumour biomarkers. The PathoBiology Group of the European Organisation for Research and Treatment of Cancer therefore has devised a standard operating procedure for the standardised preparation of human tumour tissue extracts which is designed for the quantitative analysis of tumour tissue-associated biomarkers. The easy to follow technical steps involved require 50-300 mg of deep-frozen cancer tissue placed into small size (1.2 ml) cryogenic tubes. These are placed into the shaking flask of a Mikro-Dismembrator S machine (bead mill) to pulverise the tumour tissue in the capped tubes in the deep-frozen state by use of a stainless steel ball, all within 30 s of exposure. RNA is isolated from the pulverised tissue following standard procedures. Proteins are extracted from the still frozen pulverised tissue by addition of Tris-buffered saline to obtain the cytosol fraction of the tumour or by the Tris buffer supplemented with the non-ionic detergent Triton X-100, and, after high-speed centrifugation, are found in the tissue supernatant. The resulting tissue cell debris sediment is a rich source of genomic DNA.

Endocrine tumours of the gastrointestinal tract-selected topics

This review provides an update on the pathogenesis and histopathological diagnosis of endocrine tumours of the gastrointestinal tract, concentrating on three different varieties whose careful assessment by pathologists is of particular clinical significance. These are the four types of enterochromaffin-like cell tumour of the gastric corpus, the periampullary somatostatin-containing D-cell tumour of the duodenum, and the frequently chromogranin A-negative L-cell tumour of the appendix and large intestine. In addition, the value of pathological factors in predicting the behaviour of gastrointestinal endocrine tumours and selecting therapy is discussed, and the crucial role of the pathologist in the multidisciplinary team management of these neoplasms is emphasized.