BRD4 inhibition sensitizes diffuse large B-cell lymphoma cells to ferroptosis.

Diffuse large B-cell lymphoma (DLBCL), the most common form of non-Hodgkin lymphoma, is characterized by an aggressive clinical course. In approximately one-third of patients with DLBCL, first-line multiagent immunochemotherapy fails to produce a durable response. Molecular heterogeneity and apoptosis resistance pose major therapeutic challenges in DLBCL treatment. To circumvent apoptosis resistance, the induction of ferroptosis might represent a promising strategy for lymphoma therapy. In this study, a compound library, targeting epigenetic modulators, was screened to identify ferroptosis-sensitizing drugs. Strikingly, bromodomain and extra-terminal domain (BET) inhibitors sensitized cells of the germinal center B-cell-like (GCB) subtype of DLBCL to ferroptosis induction and the combination of BET inhibitors with ferroptosis inducers, such as dimethyl fumarate or RSL3, synergized in the killing of DLBCL cells in vitro and in vivo. On the molecular level, the BET protein BRD4 was found to be an essential regulator of ferroptosis suppressor protein 1 expression and thus to protect GCB-DLBCL cells from ferroptosis. Collectively, we identified and characterized BRD4 as an important player in ferroptosis suppression in GCB-DLBCL and provide a rationale for the combination of BET inhibitors with ferroptosis-inducing agents as a novel therapeutic approach for DLBCL treatment.

Dimethyl fumarate induces ferroptosis and impairs NF-κB/STAT3 signaling in DLBCL.

Despite the development of novel targeted drugs, the molecular heterogeneity of diffuse large B-cell lymphoma (DLBCL) still poses a substantial therapeutic challenge. DLBCL can be classified into at least 2 major subtypes (germinal center B cell [GCB]-like and activated B cell [ABC]-like DLBCL), each characterized by specific gene expression profiles and mutation patterns. Here we demonstrate a broad antitumor effect of dimethyl fumarate (DMF) on both DLBCL subtypes, which is mediated by the induction of ferroptosis, a form of cell death driven by the peroxidation of phospholipids. As a result of the high expression of arachidonate 5-lipoxygenase in concert with low glutathione and glutathione peroxidase 4 levels, DMF induces lipid peroxidation and thus ferroptosis, particularly in GCB DLBCL. In ABC DLBCL cells, which are addicted to NF-κB and STAT3 survival signaling, DMF treatment efficiently inhibits the activity of the IKK complex and Janus kinases. Interestingly, the BCL-2-specific BH3 mimetic ABT-199 and an inhibitor of ferroptosis suppressor protein 1 synergize with DMF in inducing cell death in DLBCL. Collectively, our findings identify the clinically approved drug DMF as a promising novel therapeutic option in the treatment of both GCB and ABC DLBCLs.

Targeting chronic NFAT activation with calcineurin inhibitors in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) represents the most common adult lymphoma and can be divided into 2 major molecular subtypes: the germinal center B-cell-like and the aggressive activated B-cell-like (ABC) DLBCL. Previous studies suggested that chronic B-cell receptor signaling and increased NF-κB activation contribute to ABC DLBCL survival. Here we show that the activity of the transcription factor NFAT is chronically elevated in both DLBCL subtypes. Surprisingly, NFAT activation is independent of B-cell receptor signaling, but mediated by an increased calcium flux and calcineurin-mediated dephosphorylation of NFAT. Intriguingly, although NFAT is activated in both DLBCL subtypes, long-term calcineurin inhibition with cyclosporin A or FK506, both clinically approved drugs, triggers potent cytotoxicity specifically in ABC DLBCL cells. The antitumor effects of calcineurin inhibitors are associated with the reduced expression of c-Jun, interleukin-6, and interleukin-10, which were identified as NFAT target genes that are particularly important for the survival of ABC DLBCL. Furthermore, calcineurin blockade synergized with BCL-2 and MCL-1 inhibitors in killing ABC DLBCL cells. Collectively, these findings identify constitutive NFAT signaling as a crucial functional driver of ABC DLBCL and highlight calcineurin inhibition as a novel strategy for the treatment of this aggressive lymphoma subtype.

Competitive Testing of the WHO 2010 versus the WHO 2017 Grading of Pancreatic Neuroendocrine Neoplasms: Data from a Large International Cohort Study.

BACKGROUND: The World Health Organization (WHO) and the American Joint Cancer Committee (AJCC) modified the grading of pancreatic neuroendocrine neoplasms from a three-tier (WHO-AJCC 2010) to a four-tier system by introducing the novel category of NET G3 (WHO-AJCC 2017). OBJECTIVES: This study aims at validating the WHO-AJCC 2017 and identifying the most effective grading system. METHOD: A total of 2,102 patients were enrolled; entry criteria were: (i) patient underwent surgery; (ii) at least 2 years of follow-up; (iii) observation time up to 2015. Data from 34 variables were collected; grading was assessed and compared for efficacy by statistical means including Kaplan-Meier method, Cox regression analysis, Harrell's C statistics, and Royston's explained variation in univariable and multivariable analyses. RESULTS: In descriptive analysis, the two grading systems demonstrated statistically significant differences for the major category sex but not for age groups. In Cox regression analysis, both grading systems showed statistically significant differences between grades for OS and EFS; however, no statistically significant difference was observed between the two G3 classes of WHO-AJCC 2017. In multivariable analysis for the two models fitted to compare efficacy, the two grading systems performed equally well with substantially similar optimal discrimination and well-explained variation for both OS and EFS. The WHO-AJCC 2017 grading system retained statistically significant difference between the two G3 classes for OS but not for EFS. CONCLUSIONS: The WHO-AJCC 2017 grading system is at least equally performing as the WHO-AJCC 2010 but allows the successful identification of the most aggressive PanNET subgroup. Grading is confirmed as probably the most powerful tool for predicting patient survival.

The prognostic and predictive value of sstr2-immunohistochemistry and sstr2-targeted imaging in neuroendocrine tumors.

PURPOSE: Our aim was to assess the prognostic and predictive value of somatostatin receptor 2 (sstr2) in neuroendocrine tumors (NETs). METHODS: We established a tissue microarray and imaging database from NET patients that received sstr2-targeted radiopeptide therapy with yttrium-90-DOTATOC, lutetium-177-DOTATOC or alternative treatment. We used univariate and multivariate analyses to identify prognostic and predictive markers for overall survival, including sstr2-imaging and sstr2-immunohistochemistry. RESULTS: We included a total of 279 patients. In these patients, sstr2-immunohistochemistry was an independent prognostic marker for overall survival (HR: 0.82, 95 % CI: 0.67 - 0.99, n = 279, p = 0.037). In DOTATOC patients, sstr2-expression on immunohistochemistry correlated with tumor uptake on sstr2-imaging (n = 170, p < 0.001); however, sstr2-imaging showed a higher prognostic accuracy (positive predictive value: +27 %, 95 % CI: 3 - 56 %, p = 0.025). Sstr2-expression did not predict a benefit of DOTATOC over alternative treatment (p = 0.93). CONCLUSIONS: Our results suggest sstr2 as an independent prognostic marker in NETs. Sstr2-immunohistochemistry correlates with sstr2-imaging; however, sstr2-imaging is more accurate for determining the individual prognosis.

Prognostic and predictive roles of MGMT protein expression and promoter methylation in sporadic pancreatic neuroendocrine neoplasms.

BACKGROUND/AIMS: O(6)-methylguanine-methyltransferase (MGMT) is an important enzyme of DNA repair. MGMT promoter methylation is detectable in a subset of pancreatic neuroendocrine neoplasms (pNEN). A subset of pNEN responds to the alkylating agent temozolomide (TMZ). We wanted to correlate MGMT promoter methylation with MGMT protein loss in pNEN, correlate the findings with clinico-pathological data and determine the role of MGMT to predict response to TMZ chemotherapy. METHODS: We analysed a well-characterized collective of 141 resected pNEN with median follow-up of 83 months for MGMT protein expression and promoter methylation using methylation-specific PCR (MSP). A second collective of 10 metastasized, pretreated and progressive patients receiving TMZ was used to examine the predictive role of MGMT by determining protein expression and promoter methylation using primer extension-based quantitative PCR. RESULTS: In both collectives there was no correlation between MGMT protein expression and promoter methylation. Loss of MGMT protein was associated with an adverse outcome, this prognostic value, however, was not independent from grade and stage in multivariate analysis. Promoter hypermethylation was significantly associated with response to TMZ. CONCLUSION: Loss of MGMT protein expression is associated with adverse outcome in a surgical series of pNET. MGMT promoter methylation could be a predictive marker for TMZ chemotherapy in pNEN, but further, favourably prospective studies will be needed to confirm this result and before this observation can influence clinical routine.

External validation of a deep learning-based algorithm for detection of tall cells in papillary thyroid carcinoma: A multicenter study.

The tall cell subtype (TC-PTC) is an aggressive subtype of papillary thyroid carcinoma (PTC). The TC-PTC is defined as a PTC comprising at least 30% epithelial cells that are three times as tall as they are wide. In practice, this definition is difficult to adhere to, resulting in high inter-observer variability. In this multicenter study, we validated a previously trained deep learning (DL)-based algorithm for detection of tall cells on 160 externally collected hematoxylin and eosin (HE)-stained PTC whole-slide images. In a test set of 360 manual annotations of regions of interest from 18 separate tissue sections in the external dataset, the DL-based algorithm detected TCs with a sensitivity of 90.6% and a specificity of 88.5%. The DL algorithm detected non-TC areas with a sensitivity of 81.6% and a specificity of 92.9%. In the validation datasets, 20% and 30% TC thresholds correlated with a significantly shorter relapse-free survival. In conclusion, the DL algorithm detected TCs in unseen, external scanned HE tissue slides with high sensitivity and specificity without any retraining.

ISL1 expression is not restricted to pancreatic well-differentiated neuroendocrine neoplasms, but is also commonly found in well and poorly differentiated neuroendocrine neoplasms of extrapancreatic origin.

The human insulin gene enhancer-binding protein islet-1 (ISL1) is a transcription factor involved in the differentiation of the neuroendocrine pancreatic cells. Recent studies identified ISL1 as a marker for pancreatic well-differentiated neuroendocrine neoplasms. However, little is known about ISL1 expression in pancreatic poorly differentiated and in extrapancreatic well and poorly differentiated neuroendocrine neoplasms. We studied the immunohistochemical expression of ISL1 in 124 neuroendocrine neoplasms. Among pancreatic neuroendocrine neoplasms, 12/13 with poor differentiation were negative, whereas 5/7 with good differentiation but a Ki67 >20% were positive. In extrapancreatic neuroendocrine neoplasms, strong positivity was found in Merkel cell carcinomas (25/25), pulmonary small cell neuroendocrine carcinomas (21/23), medullary thyroid carcinomas (9/9), paragangliomas/pheochromocytomas (6/6), adrenal neuroblastomas (8/8) and head and neck neuroendocrine carcinomas (4/5), whereas no or only weak staining was recorded in pulmonary carcinoids (3/15), olfactory neuroblastomas (1/4) and basaloid head and neck squamous cell carcinomas (0/15). ISL1 stained the neuroendocrine carcinoma component of 5/8 composite carcinomas and also normal neuroendocrine cells in the thyroid, adrenal medulla, stomach and colorectum. Poorly differentiated neuroendocrine neoplasms, regardless of their ISL1 expression, were usually TP53 positive. Our results show the almost ubiquitous expression of ISL1 in extrapancreatic poorly differentiated neuroendocrine neoplasms and neuroblastic malignancies and its common loss in pancreatic poorly differentiated neuroendocrine neoplasms. These findings modify the role of ISL1 as a marker for pancreatic neuroendocrine neoplasms and suggest that ISL1 has a broader involvement in differentiation and growth of neuroendocrine neoplasms than has so far been assumed.

Diagnostic and prognostic implications of the PAX8-PPARγ translocation in thyroid carcinomas-a TMA-based study of 226 cases.

AIMS: Follicular thyroid carcinoma (FTC) has been a diagnostic challenge for decades. The PAX8-PPARγ rearrangement has been detected in FTC and classic papillary thyroid carcinomas (PTCs). The aims of this study were to assess the presence of PAX8-PPARγ by using tissue microarrays in a large cohort of different thyroid neoplasms, and to assess its diagnostic and prognostic implications. METHODS AND RESULTS: Fluorescence in-situ hybridization (FISH) analysis for PAX8-PPARγ was performed on 226 thyroid tumours, comprising FTCs (n = 59), PTCs (n = 126), poorly differentiated thyroid carcinomas (PDs; n = 34), follicular thyroid adenomas (FTAs; n = 5), and follicular tumours of unknown malignant potential (FTUMPs; n = 2). PAX8-PPARγ was detected in 12% of FTCs, 1% of PTCs, 7% of PDs, and in both cases of FTUMP. There was no correlation between the extent of capsular or vascular invasion and PAX8-PPARγ, or between lymph node or haematogenous metastasis and PAX8-PPARγ. Overall survival (OS), tumour-specific survival (TSS) and relapse-free-survival (RFS) were not influenced by PAX8-PPARγ. CONCLUSIONS: In this study, we demonstrate for the first time the presence of PAX8-PPARγ in PDs and FTUMPs, whereas in FTCs and PTCs the prevalence of PAX8-PPARγ is lower than previously reported. PAX8-PPARγ did not correlate with invasiveness or affect prognosis in any tumour type.

Inhibition of glutaminase-1 in DLBCL potentiates venetoclax-induced antitumor activity by promoting oxidative stress.

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma in adults, but first-line immunochemotherapy fails to produce a durable response in about one-third of the patients. Because tumor cells often reprogram their metabolism, we investigated the importance of glutaminolysis, a pathway converting glutamine to generate energy and various metabolites, for the growth of DLBCL cells. Glutaminase-1 (GLS1) expression was robustly detected in DLBCL biopsy samples and cell lines. Both pharmacological inhibition and genetic knockdown of GLS1 induced cell death in DLBCL cells regardless of their subtype classification, whereas primary B cells remained unaffected. Interestingly, GLS1 inhibition resulted not only in reduced levels of intermediates of the tricarboxylic acid cycle but also in a strong mitochondrial accumulation of reactive oxygen species. Supplementation of DLBCL cells with α-ketoglutarate or with the antioxidant α-tocopherol mitigated oxidative stress and abrogated cell death upon GLS1 inhibition, indicating an essential role of glutaminolysis in the protection from oxidative stress. Furthermore, the combination of the GLS1 inhibitor CB-839 with the therapeutic BCL2 inhibitor ABT-199 not only induced massive reactive oxygen species (ROS) production but also exhibited highly synergistic cytotoxicity, suggesting that simultaneous targeting of GLS1 and BCL2 could represent a novel therapeutic strategy for patients with DLBCL.

Extranodal diffuse large B cell lymphoma of cutaneous follicle centre lymphoma type: a study of 24 patients with non-cutaneous primary limited stage extranodal diffuse large B cell lymphoma in support of a new concept.

AIMS: Follicle centre cell lymphoma of small cell type showing either a follicular or diffuse growth pattern similar to cutaneous follicle centre lymphoma (cFCL) has been recognized in extranodal non-cutaneous sites. Our aim was (i) to investigate whether diffuse large B cell lymphoma (DLBCL) of cFCL type could be identified in extranodal non-cutaneous sites and (ii) whether clinical characteristics similar to primary cFCL could be recognized. METHODS AND RESULTS: Of 24 extranodal non-cutaneous DLBCLs, nine (38%) had large centrocytoid morphology and 15 (62%) were either 'centrocytoid and centroblastic' or 'centroblastic and immunoblastic'. Six centrocytoid cases were Irf-4 negative, Bcl-6 positive and at most weakly CD10- or Bcl-2-positive by immunohistochemistry, consistent with DLBCL of cFCL type. All patients with cFCL type were stage IE and were significantly younger than other patients. Recurrences occurred in two patients and were exclusively extranodal. CONCLUSION: Our results suggest that DLBCL of cFCL type can be identified in extranodal non-cutaneous sites and shows clinical characteristics similar to genuine cFCL. We propose to expand the concept of cFCL to encompass large cell lymphomas in extranodal sites.

Poorly differentiated oncocytic thyroid carcinoma--diagnostic implications and outcome.

AIMS: Poorly differentiated thyroid carcinomas (PDTC) are an ongoing diagnostic challenge. Although the Turin consensus criteria for PDTC excluded consideration of oncocytic tumours, the World Health Organization (WHO) classification does recognise an oncocytic variant of conventional PDTC. The aims of this study were to establish whether the Turin criteria can be applied to oncocytic PDTC, and to determine if there are prognostic differences between conventional and oncocytic PDTC. METHODS AND RESULTS: We applied the Turin criteria to 129 thyroid carcinomas. We identified 18 oncocytic PDTC and 16 conventional PDTC. Kaplan-Meier analysis revealed a significantly worse outcome for oncocytic PDTC with regard to overall and tumour-specific survival but no difference for relapse-free survival, all of which were confirmed by multivariate analysis. There was no association of survival with gender, age or tumour stage. CONCLUSIONS: The Turin criteria can be applied to oncocytic PDTC and patients with this variant have a decreased survival using conventional radioiodine treatment compared to conventional PDTC and might therefore be candidates for novel treatment modalities.

The Paracaspase MALT1 in Cancer.

Almost twenty years ago, the importance of the paracaspase MALT1 in antigen receptor-induced NF-κB activation was first described. Since then, several other immune receptors, G-protein-coupled receptors, and receptor tyrosine kinases were identified as relying on MALT1 to induce NF-κB activation. In various hematological malignancies and solid tumors, MALT1 is constitutively activated and drives chronic NF-κB target gene expression. Deregulated MALT1 activity in cancer thus promotes tumor cell survival, proliferation, and metastasis. Since the molecular function of MALT1 partially requires its protease activity, pharmacological targeting of MALT1 may represent a promising anti-cancer strategy. Here, we review the molecular features of MALT1 activation and function as well as the therapeutic potential of MALT1 inhibition in hematological malignancies and solid tumors.

Clinical aspects, diagnostic challenges and management of patients with neuroendocrine tumors (NETs).

Neuroendocrine tumor (NET) entities are rare malignancies. Higher awareness and improved diagnostic methods have led to an increasing incidence of these diseases, and most oncologists deal with such patients in their daily practice. The symposium on NETs that was held in Merano (Italy) in October 2009 was organized by the German-speaking European School of Oncology (dESO) and gathered specialists from different disciplines of transalpine countries to bring together experiences and observations regarding these tumors. The goal of the meeting and of this review was to illustrate both well- and poorly differentiated NETs and to encourage interdisciplinary approaches.

Ferroptotic pores induce Ca2+ fluxes and ESCRT-III activation to modulate cell death kinetics.

Ferroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. Despite its key role in the inflammatory outcome of ferroptosis, little is known about the molecular events leading to the disruption of the plasma membrane during this type of cell death. Here we show that a sustained increase in cytosolic Ca2+ is a hallmark of ferroptosis that precedes complete bursting of the cell. We report that plasma membrane damage leading to ferroptosis is associated with membrane nanopores of a few nanometers in radius and that ferroptosis, but not lipid peroxidation, can be delayed by osmoprotectants. Importantly, Ca2+ fluxes during ferroptosis induce the activation of the ESCRT-III-dependent membrane repair machinery, which counterbalances the kinetics of cell death and modulates the immunological signature of ferroptosis. Our findings with ferroptosis provide a unifying concept that sustained increase of cytosolic Ca2+ prior to plasma membrane rupture is a common feature of regulated types of necrosis and position ESCRT-III activation as a general protective mechanism in these lytic cell death pathways.

Borrelia in granuloma annulare, morphea and lichen sclerosus: a PCR-based study and review of the literature.

BACKGROUND: Morphea, granuloma annulare (GA) and lichen sclerosus et atrophicans (LSA) have also been suggested to be linked to Borrelia infection. Previous studies based on serologic data or detection of Borrelia by immunohistochemistry and polymerase chain reaction (PCR) reported contradictory results. Thus, we examined skin biopsies of morphea, GA and LSA by PCR to assess the prevalence of Borrelia DNA in an endemic area and to compare our results with data in the literature. METHODS: Amplification of DNA sequences of Borrelia burgdorferi sensu lato by nested PCR from formalin-fixed and paraffin-embedded skin biopsies of morphea, GA and LSA, followed by automated sequencing of amplification products. PCR-based studies on Borrelia species in these disorders published until July 2009 were retrieved by a literature search. RESULTS: Borrelia DNA was detected in 3 of 112 skin biopsies (2.7%) including one of 49 morphea biopsies (2.0%), one of 48 GA biopsies (2.1%) and one of 15 LSA biopsies (6.6%). Amplification products belonged to B. burgdorferi sensu stricto in two cases available for sequence analysis. CONCLUSIONS: The results of our and most of other PCR-based studies do not argue for a significant association of B. burgdorferi sensu lato with morphea, GA, LSA.

[Pathology of malignant lymphomas--clarity instead of confusion]. / Pathologie maligner Lymphome--Klarheit statt Wirrwarr.

After decades of confusion in lymphoma classification clearness was achieved with the publication of the REAL classification 1994 and of the WHO classification 2001. The revised 4th edition 2008 features some additional new categories. The WHO classification comprises B- and T-lymphoblastic neoplasms, mature B-cell lymphomas, mature T-cell and NK-cell lymphomas and Hodgkin lymphomas. A modern diagnostic work-up of lymphomas is based on morphology, immunohistochemistry and increasingly on molecular studies. Last but not least the evaluation of all these findings by an expert haematopathologist, who collaborates closely with the treating clinicians, is essential. The aim is to give an overview of the most frequent mature B-cell lymphomas and the most important classical Hodgkin lymphomas with focus on morphology and immunohistochemistry.

Ultrafast Toluidine Blue Staining for Rapid On-Site Evaluation of Cytological Smears.

Rapid on-site evaluation (ROSE) is one of cytopathology's "unique selling propositions." The quality, speed, and ease of handling of the staining used is a critical factor for the efficacy of the ROSE procedure. Here, we describe a modification of rapid toluidine blue staining that can be performed within 25 s, provides excellent nuclear morphology, and is compatible with subsequent Papanicolaou staining of the slides. Furthermore, exposure to hazardous chemicals is minimized, as no organic solvents other than the alcohol-based fixative and glycerin for temporary mounting and coverslipping are required. We have used this protocol successfully in our ROSE practice and have not observed any discrepancies between toluidine blue- and permanent Papanicolaou-stained slides.

Threonine Phosphorylation of IκBζ Mediates Inhibition of Selective Proinflammatory Target Genes.

Transcription factors of the NF-κB family play a crucial role for immune responses by activating the expression of chemokines, cytokines, and antimicrobial peptides involved in pathogen clearance. IκBζ, an atypical nuclear IκB protein and selective coactivator of particular NF-κB target genes, has recently been identified as an essential regulator for skin immunity. This study discovered that IκBζ is strongly induced in keratinocytes that sense the fungal glucan zymosan A. Additionally, IκBζ is essential for the optimal expression of proinflammatory genes, such as IL6, CXCL5, IL1B, or S100A9. Moreover, this study found that IκBζ was not solely regulated on the transcriptional level but also by phosphorylation events. This study identified several IκBζ phosphorylation sites, including a conserved cluster of threonine residues located in the N-terminus of the protein, which can be phosphorylated by MAPKs. Surprisingly, IκBζ phosphorylation at this threonine cluster promoted the recruitment of histone deacetylase 1 to specific target gene promoters and, thus, negatively controlled transcription. Taken together, this study proposes a model of how an antifungal response translates to the expression of proinflammatory cytokines and highlights an additional layer of complexity in the regulation of the NF-κB responses in keratinocytes.

Glucagon cell adenomatosis: a newly recognized disease of the endocrine pancreas.

BACKGROUND: Glucagon-producing tumors are either solitary neoplasms of the pancreas, occasionally associated with a glucagonoma syndrome, or multiple neoplasms associated with multiple endocrine neoplasia type 1 (MEN1). We observed a previously undescribed multicentric glucagon-producing tumor disease that is not related to MEN1. METHODS: Pancreatic tissue from four patients showing multiple neuroendocrine microadenomas and in two cases also macrotumors were screened for hormones using immunohistochemical and morphometric methods. MEN1, von Hippel-Lindau, and p27 germ line and somatic mutation analysis was performed. Deletion of MEN1 (11q13), von Hippel-Lindau (3p25), and the centromere 11 and 3 gene locus was determined by fluorescence in situ hybridization. DNA copy number changes were studied using array comparative genomic hybridization. RESULTS: The pancreatic tissue from the four patients contained more than 870 microadenomas and 10 macrotumors, all of which expressed exclusively glucagon and none of which showed evidence of malignancy. In addition, many islets were unusually large and showed glucagon cell hyperplasia. There was no clinical or molecular evidence of any hereditary tumor disease, and changes in the MEN1 gene were only seen in individual tumors. Array comparative genomic hybridization of one macrotumor and 20 pooled microadenomas revealed a homogeneous diploid chromosome set. CONCLUSIONS: The findings are sufficiently distinctive to suggest a new neoplastic disease of the endocrine pancreas that we recommend calling glucagon cell adenomatosis. Clinically, this disease may be an incidental finding, or it may lead to a glucagonoma syndrome.