Laura H. Tang

DAXX/ATRX, MEN1, and mTOR pathway genes are frequently altered in pancreatic neuroendocrine tumors.

A rare but deadly form of human pancreatic cancer harbors mutations in chromatin remodeling genes. Pancreatic neuroendocrine tumors (PanNETs) are a rare but clinically important form of pancreatic neoplasia. To explore the genetic basis of PanNETs, we determined the exomic sequences of 10 nonfamilial PanNETs and then screened the most commonly mutated genes in 58 additional PanNETs. The most frequently mutated genes specify proteins implicated in chromatin remodeling: 44% of the tumors had somatic inactivating mutations in MEN1, which encodes menin, a component of a histone methyltransferase complex, and 43% had mutations in genes encoding either of the two subunits of a transcription/chromatin remodeling complex consisting of DAXX (death-domain–associated protein) and ATRX (α thalassemia/mental retardation syndrome X-linked). Clinically, mutations in the MEN1 and DAXX/ATRX genes were associated with better prognosis. We also found mutations in genes in the mTOR (mammalian target of rapamycin) pathway in 14% of the tumors, a finding that could potentially be used to stratify patients for treatment with mTOR inhibitors.

Clinically aggressive solid pseudopapillary tumors of the pancreas: a report of two cases with components of undifferentiated carcinoma and a comparative clinicopathologic analysis of 34 conventional cases.

Solid pseudopapillary tumors (SPTs) are unusual neoplasms of the pancreas of uncertain histogenesis that occur mostly, but not exclusively, in young women. The pathologic features and immunophenotype of SPT are unique and well characterized. Despite its low malignant potential, proximately 15% of patients with SPT develop metastatic disease, mostly involving the liver or peritoneum. Even in the presence of disseminated disease, the clinical course is usually protracted, and the overall 5-year survival is reportedly 97%. We have encountered 2 cases of SPT possessing unusual pathologic features and exhibiting an aggressive clinical course. At the time of presentation, 1 patient had liver metastasis, and the other had a lymph node metastasis and developed liver metastases within 3 months. Both died of disease at 6 and 16 months, respectively, following the initial diagnosis. Review of other cases of SPT treated at Memorial Sloan-Kettering Cancer Center (New York, NY) revealed that 5 of 34 cases (15%) with conventional histologic features developed liver metastases. In contrast to the 2 cases reported here, all 5 patients survived for a mean of 106 months (39-193 months), and only 2 died of disease 5 and 10 years, respectively, following the initial resection. The pathologic features of the two rapidly fatal cases, which might have been indicative of their aggressive behavior, included a diffuse growth pattern, extensive tumor necrosis, significant nuclear atypia, an unusually high mitotic rate (35-70/50 high power fields), and in one a component of sarcomatoid carcinoma. However, regions displaying the typical histologic features of SPT were also evident. Abnormal β-catenin distribution and markedly increased MIB1 expression were detected by immunohistochemistry in both cases. The immunohistochemical staining patterns were otherwise similar to those of conventional SPTs. Although precise pathologic criteria suggesting a high risk for aggressive behavior are uncertain, recognition of some of the unusual pathologic features displayed in these 2 cases may be useful in the prediction of potentially more aggressive SPTs. The possibility that these tumors represent high-grade malignant transformation of a conventional low-grade SPT is proposed.

Pathology reporting of neuroendocrine tumors : application of the Delphic consensus process to the development of a minimum pathology data set

Epithelial neuroendocrine tumors (NETs) have been the subject of much debate regarding their optimal classification. Although multiple systems of nomenclature, grading, and staging have been proposed, none has achieved universal acceptance. To help define the underlying common features of these classification systems and to identify the minimal pathology data that should be reported to ensure consistent clinical management and reproducibility of data from therapeutic trials, a multidisciplinary team of physicians interested in NETs was assembled. At a group meeting, the participants discussed a series of “yes” or “no” questions related to the pathology of NETs and the minimal data to be included in the reports. After discussion, anonymous votes were taken, using the Delphic principle that 80% agreement on a vote of either yes or no would define a consensus. Questions that failed to achieve a consensus were rephrased once or twice and discussed, and additional votes were taken. Of 108 questions, 91 were answerable either yes or no by more than 80% of the participants. There was agreement about the importance of proliferation rate for tumor grading, the landmarks to use for staging, the prognostic factors assessable by routine histology that should be reported, the potential for tumors to progress biologically with metastasis, and the current status of advanced immunohistochemical and molecular testing for treatment-related biomarkers. The lack of utility of a variety of immunohistochemical stains and pathologic findings was also agreed upon. A consensus could not be reached for the remaining 17 questions, which included both minor points related to extent of disease assessment and some major areas such as terminology, routine immunohistochemical staining for general neuroendocrine markers, use of Ki67 staining to assess proliferation, and the relationship of tumor grade to degree of differentiation. On the basis of the results of the Delphic voting, a minimum pathology data set was developed. Although there remains disagreement among experts about the specific classification system that should be used, there is agreement about the fundamental pathology data that should be reported. Examination of the areas of disagreement reveals significant opportunities for collaborative study to resolve unanswered questions.

PEGylated Gold Nanoparticles Conjugated to Monoclonal F19 Antibodies as Targeted Labeling Agents for Human Pancreatic Carcinoma Tissue

In this study, we describe optical detection of antibody-conjugated nanoparticles bound to surgically resected human pancreatic cancer tissue. Gold nanoparticles stabilized by heterobifunctional polyethylene glycol (PEG) were prepared using approximately 15 nm spherical gold cores and covalently coupled to F19 monoclonal antibodies. The heterobifunctional PEG ligands contain a dithiol group for stable anchoring onto the gold surface and a terminal carboxy group for coupling of antibodies to the outside of the PEG shell. The nanoparticle-antibody bioconjugates form highly stable dispersions and exhibit long-term resistance to agglomeration. This has been demonstrated by dynamic light scattering, size exclusion chromatography, and transmission electron microscopy. The nanoparticle bioconjugates were used to label tumor stroma in approximately 5 mum thick sections of resected human pancreatic adenocarcinoma. After rinsing away nonbound nanoparticles and fixation, the tissue samples were imaged by darkfield microscopy near the nanoparticle resonance scattering maximum (approximately 560 nm). The images display pronounced tissue features and suggest that this novel labeling method could provide for facile identification of cancer tissue. Tumor samples treated with gold nanoparticles conjugated to nonspecific control antibodies and noncancerous pancreatic tissue treated with mAb-F19-conjugated gold nanoparticles both exhibited correctly negative results and showed no tissue staining.

Small cell and large cell neuroendocrine carcinomas of the pancreas are genetically similar and distinct from well-differentiated pancreatic neuroendocrine tumors

Poorly differentiated neuroendocrine carcinomas (NECs) of the pancreas are rare malignant neoplasms with a poor prognosis. The aim of this study was to determine the clinicopathologic and genetic features of poorly differentiated NECs and compare them with other types of pancreatic neoplasms. We investigated alterations of KRAS, CDKN2A/p16, TP53, SMAD4/DPC4, DAXX, ATRX, PTEN, Bcl2, and RB1 by immunohistochemistry and/or targeted exomic sequencing in surgically resected specimens of 9 small cell NECs, 10 large cell NECs, and 11 well-differentiated neuroendocrine tumors (PanNETs) of the pancreas. Abnormal immunolabeling patterns of p53 and Rb were frequent (p53, 18 of 19, 95%; Rb, 14 of 19, 74%) in both small cell and large cell NECs, whereas Smad4/Dpc4, DAXX, and ATRX labeling was intact in virtually all of these same carcinomas. Abnormal immunolabeling of p53 and Rb proteins correlated with intragenic mutations in the TP53 and RB1 genes. In contrast, DAXX and ATRX labeling was lost in 45% of PanNETs, whereas p53 and Rb immunolabeling was intact in these same cases. Overexpression of Bcl-2 protein was observed in all 9 small cell NECs (100%) and in 5 of 10 (50%) large cell NECs compared with only 2 of 11 (18%) PanNETs. Bcl-2 overexpression was significantly correlated with higher mitotic rate and Ki67 labeling index in neoplasms in which it was present. Small cell NECs are genetically similar to large cell NECs, and these genetic changes are distinct from those reported in PanNETs. The finding of Bcl-2 overexpression in poorly differentiated NECs, particularly small cell NEC, suggests that Bcl-2 antagonists/inhibitors may be a viable treatment option for these patients.

Molecular Classification of Gastric Cancer: A New Paradigm

Purpose: Gastric cancer may be subdivided into 3 distinct subtypes—proximal, diffuse, and distal gastric cancer—based on histopathologic and anatomic criteria. Each subtype is associated with unique epidemiology. Our aim is to test the hypothesis that these distinct gastric cancer subtypes may also be distinguished by gene expression analysis. Experimental Design: Patients with localized gastric adenocarcinoma being screened for a phase II preoperative clinical trial (National Cancer Institute, NCI #5917) underwent endoscopic biopsy for fresh tumor procurement. Four to 6 targeted biopsies of the primary tumor were obtained. Macrodissection was carried out to ensure more than 80% carcinoma in the sample. HG-U133A GeneChip (Affymetrix) was used for cDNA expression analysis, and all arrays were processed and analyzed using the Bioconductor R-package. Results: Between November 2003 and January 2006, 57 patients were screened to identify 36 patients with localized gastric cancer who had adequate RNA for expression analysis. Using supervised analysis, we built a classifier to distinguish the 3 gastric cancer subtypes, successfully classifying each into tightly grouped clusters. Leave-one-out cross-validation error was 0.14, suggesting that more than 85% of samples were classified correctly. Gene set analysis with the false discovery rate set at 0.25 identified several pathways that were differentially regulated when comparing each gastric cancer subtype to adjacent normal stomach. Conclusions: Subtypes of gastric cancer that have epidemiologic and histologic distinctions are also distinguished by gene expression data. These preliminary data suggest a new classification of gastric cancer with implications for improving our understanding of disease biology and identification of unique molecular drivers for each gastric cancer subtype. Clin Cancer Res; 17(9); 2693–701. ©2011 AACR.

Effect of tumor heterogeneity on the assessment of Ki67 labeling index in well-differentiated neuroendocrine tumors metastatic to the liver: implications for prognostic stratification.

The Ki67 labeling index is known to correlate with survival in patients with neuroendocrine tumors (NETs). A grading scheme recently endorsed by the World Health Organization for gastroenteropancreatic NETs classifies well-differentiated NETs into 2 categories based on the Ki67 labeling index: low (G1) and intermediate grades (G2). Tumor heterogeneity is a common finding in many tumors including NETs. Metastatic NETs to the liver are often diagnosed by radiographically guided needle core biopsy from which the Ki67 index is determined, which randomly samples the lesion without being targeted to regions that may show a higher proliferative rate. Whether the Ki67 index obtained from this type of limited material represents the whole tumor has been questioned. Forty-five surgically resected liver metastases of well-differentiated NETs were retrieved. A 9 core (3 core-triplets) tissue microarray (TMA) was constructed from the paraffin blocks of each tumor, each triplet considered to represent a virtual biopsy. Immunohistochemical staining for Ki67 was performed on TMA and whole slides, and the Ki67 labeling indices were determined by digital image analysis. Correlation of the Ki67 index with patient survival was analyzed. Forty-seven percent of cases showed intratumoral heterogeneity in Ki67 index that translated into discrepant grades among subsections on the whole slide. A similar trend was recapitulated on the virtual biopsies, although to a lesser degree. When the definitive grade of the tumor was based on the highest Ki67 index identified on the whole slide, the virtual biopsies perfectly predicted G1 cases (100%), but were much less accurate for G2 cases (47.8% with 3 biopsies and 34.8% with single biopsy). Accordingly, the predictive value for G1 on the virtual biopsies was low (64.7% and 59.5% for 3 and 1 biopsy, respectively), but was perfect for G2 (100%). By Kaplan-Meier survival analysis, there was a statistically significant difference between G1 and G2 in terms of overall survival, disease-free survival, and progression-free survival when graded on either whole-slide subsections or virtual biopsies. On the whole slides, the highest Ki67 grade showed a better correlation with overall survival than the mean Ki67 grade. In summary, by image analysis, we found that about half of the NETs metastatic to the liver show intratumoral heterogeneity resulting in discrepant Ki67 grade. In most cases, in particular G1, the virtual biopsy is representative of the whole slide, but for G2 the representation is <50%. Nevertheless, grades based on virtual biopsy had statistically significant prognostic values on patient survival, and there is no clear difference between the 3 and single virtual biopsy. Ki67 staining of core biopsies usually provides an adequately reliable method of proliferation assessment for prognosis of metastatic NETs to the liver, although the choice of treatment may be affected by intratumoral grade heterogeneity.

Helicobacter pylori alters gastric epithelial cell cycle events and gastrin secretion in Mongolian gerbils

BACKGROUND & AIMS Human colonization with Helicobacter pylori increases the risk for distal gastric adenocarcinoma, possibly by altering gastric epithelial cell cycle events and/or gastrin secretion. This study aimed to determine whether H. pylori virulence-related characteristics affect apoptosis, proliferation, and gastrin levels in a rodent model of gastric adenocarcinoma. METHODS Mongolian gerbils were challenged with H. pylori wild-type or isogenic cagA(-) and vacA(-) mutants, and apoptotic and proliferating cells were identified by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and proliferating cell nuclear antigen immunohistochemistry, respectively. Serum gastrin levels were determined by radioimmunoassay. RESULTS Gastric epithelial cell turnover was no different after infection with the wild-type, cagA(-), or vacA(-) strains. H. pylori infection significantly increased antral apoptosis 2-4 weeks after challenge, before apoptotic indices decreased to baseline. In contrast, antral proliferation rates were significantly higher 16-20 weeks after inoculation, but then decreased by 40 weeks. Antral proliferation was significantly related to serum gastrin levels, whereas antral apoptosis was inversely related to acute inflammation and lymphoid follicles. CONCLUSIONS In H. pylori-infected gerbils, enhanced antral apoptosis is an early and transient cell cycle event. Epithelial cell proliferation peaks later and is significantly related to increased gastrin levels, suggesting that epithelial cell growth in H. pylori-colonized mucosa may be mediated by gastrin-dependent mechanisms.

Pathologic Classification and Clinical Behavior of the Spectrum of Goblet Cell Carcinoid Tumors of the Appendix

Appendiceal tumors exhibiting both neuroendocrine and glandular differentiation are uncommon and have caused difficulty in pathologic classification, prediction of prognosis, and clinical management. Previously, such lesions have been variously designated as adenocarcinoid, goblet cell carcinoid (GCC), and mixed adenocarcinoma carcinoid. In this study, we undertook a retrospective investigation of 63 such cases and classified them as typical GCC (group A) and adenocarcinoma ex GCC on the basis of the histologic features of the tumor at the primary site. The adenocarcinoma ex GCC group was further divided into signet ring cell type (group B) and poorly differentiated adenocarcinoma type (group C). The clinical characteristics and prognosis were compared within these groups and with conventional de novo appendiceal adenocarcinomas. Both groups A and B tumors shared a similar immunoprofile, which included generally focal immunoreactivity for neuroendocrine markers, and a normal intestinal type mucin glycoprotein profile (negative MUC1 expression and preserved MUC2 immunoreactivity). The proliferative index was relatively low in these tumors and slightly increased from groups A to B tumors (11% to 16%). Both β-catenin and E-cadherin exhibited a normal membranous staining pattern in groups A and B tumors. The poorly differentiated adenocarcinomas ex GCC (group C) demonstrated abnormal p53 and β-catenin immunoreactivity. The mean follow-up time was 49±5 (SE) months. The overall disease-specific survival for all subtypes was 77%, with 46% of patients without evidence of disease and 31% alive with disease. The mean survival was 43±7 months. All the patients with clinical stage of I or IIA disease had a favorable outcome after appropriate surgery with or without chemotherapy. Although most patients (63%) with GCC presented at an advanced clinical stage, their clinical outcome could be differentiated by subclassification of tumors. The stage IV-matched 5-year survival was 100%, 38%, and 0% for groups A, B, and C, respectively. In conclusion, GCC is a distinctive appendiceal neoplasm that exhibits unique pathologic features and clinical behavior. They display a spectrum of histologic features and possess the potential to transform to an adenocarcinoma phenotype of either signet ring cell or poorly differentiated adenocarcinoma types. Careful evaluation of the morphologic features of GCCs and appropriate pathologic classification are crucial for clinical management and prediction of outcome. Surgical management with right hemicolectomy is recommended after appendectomy for most cases, particularly those with an adenocarcinoma component (groups B and C).

Objective quantification of the Ki67 proliferative index in neuroendocrine tumors of the gastroenteropancreatic system: a comparison of digital image analysis with manual methods.

Pathologic grading for prognostic stratification of neuroendocrine tumors (NETs) is critical but presents a challenging interpretive dilemma. Tumor cell proliferative rate is an important factor in the determination of prognosis, and immunohistochemical analysis with Ki67 is becoming more widely used to quantify the proliferative rate. However, Ki67 assessment has limitations due to lack of uniformity and consistency in quantification. These limitations are accentuated in well-differentiated NETs, as differences in the range of 1% to 5% can alter tumor grade, with potential implications for treatment. We therefore performed a concordance study to assess different Ki67 quantification techniques including: (a) digital image analysis (DIA); (b) manual counting (MC) of >2000 cells; and (c) “eyeballed” estimate (EE) of labeling percentage by pathologists (n=18), including individuals experienced in evaluating Ki67 labeling as well as others who had little prior experience assessing Ki67 percentages. Forty-five Ki67 images were selected and analyzed using the 3 methods. On the basis of the recommendations of the World health Organization (WHO) for grading NETs, MC of 2000 cells was used as the “gold standard” reference against which the other techniques were compared. Three images were presented twice, the second being inverted, to assess intraobserver consistency. Statistical analyses were performed to evaluate: (a) the concordance between methods; (b) intraobserver and interobserver consistency; and (c) correlation of NET grades on the basis of Ki67 scores by EE versus the gold standard. Agreement between scores was assessed by intraclass correlation (ICC). DIA and MC were highly concordant (ICC=0.98). The ICC between DIA and the mean EE of all observers was 0.88. However, there was discordance among individual observers on all cases quantified by EE (ICC=0.13). The ICC for intraobserver consistency was 0.39±0.26. With Ki67 in the ranges of <1%, 2% to 3%, and >20%, the mean of Ki67 by EE was, respectively, 93%±2%, 55%±7%, and 55%±15% correct against the gold standard. The &kgr; statistics for EE exhibited low agreement (&kgr;=0.24; 95% confidence interval, 0.23-0.25) for all WHO NET grades. Incorrect assessment by EE resulted in upgrading of all WHO G1 group tumors (n=14); in the WHO G2 group, downgrading of 41% cases occurred (n=11) when Ki67 was <5% (by DIA or MC), and upgrading of 59% cases occurred (n=16) when Ki67 was >5%. We conclude that DIA and MC are the acceptable standards for Ki67 assessment. Given the inherent discordance in determining the grade, the use of an approximate EE of the Ki67-labeling index requires critical reevaluation, especially for NETs with a labeling index straddling the cut-points between grades. Consequently, determination of therapeutic strategies should be guided by an amalgamation of clinicopathologic characteristics, including but not limited to the Ki67 index.