High tumour mutational burden and EGFR/MAPK pathway activation are therapeutic targets in metastatic porocarcinoma.

BACKGROUND: Eccrine porocarcinoma (EPC) is a rare skin cancer arising from the eccrine sweat glands. Due to the lack of effective therapies, metastasis is associated with a high mortality rate. OBJECTIVES: To investigate the drivers of EPC progression. METHODS: We carried out genomic and transcriptomic profiling of metastatic EPC (mEPC), validation of the observed alterations in an EPC patient-derived cell line, confirmation of relevant observations in a large patient cohort of 30 tumour tissues, and successful treatment of a patient with mEPC under the identified treatment regimens. RESULTS: mEPC was characterized by a high tumour mutational burden (TMB) with an ultraviolet signature, widespread copy number alterations and gene expression changes that affected cancer-relevant cellular processes such as cell cycle regulation and proliferation, including a pathogenic TP53 (tumour protein 53) mutation, a copy number deletion in the CDKN2A (cyclin dependent kinase inhibitor 2A) region and a CTNND1/PAK1 [catenin delta 1/p21 (RAC1) activated kinase 1] gene fusion. The overexpression of EGFR (epidermal growth factor receptor), PAK1 and MAP2K1 (mitogen-activated protein kinase kinase 1; also known as MEK1) genes translated into strong protein expression and respective pathway activation in the tumour tissue. Furthermore, a patient-derived cell line was sensitive to EGFR and MEK inhibition, confirming the functional relevance of the pathway activation. Immunohistochemistry analyses in a large patient cohort showed the relevance of the observed changes to the pathogenesis of EPC. Our results indicate that mEPC should respond to immune or kinase inhibitor therapy. Indeed, the advanced disease of our index patient was controlled by EGFR-directed therapy and immune checkpoint inhibition for more than 2 years. CONCLUSIONS: Molecular profiling demonstrated high TMB and EGFR/MAPK pathway activation to be novel therapeutic targets in mEPC.

Management of patients with pancreatic cystic lesions: A case-based survey.

BACKGROUND: Pancreatic cystic lesions (PCL), including intraductal papillary mucinous neoplasia (IPMN), harbor different malignant potential and the optimal management is often challenging. The present study aims to depict the compliance of experts with current consensus guidelines and the accuracy of treatment recommendations stratified by the medical specialty and hospital volume. METHODS: An international survey was conducted using a set of 10 selected cases of PCL that were presented to a cohort of international experts on pancreatology. All presented cases were surgically resected between 2004 and 2015 and histopathological examination was available. Accuracy of the treatment recommendations was based on the European and international consensus guideline algorithms, and the histopathological result. RESULTS: The response rate of the survey was 26% (46 of 177 contacted experts), consisting of 70% surgeons and 30% gastroenterologists/oncologists (GI/Onc). In the case of main-duct IPMN (MD-IPMN), surgeons preferred more often the surgical approach in comparison with the GI/Onc (55 versus 44%). The mean accuracy rate based on the European and international consensus guidelines, and the histopathological result, were 71/76/38% (surgeons), and 70/73/34% (GI/Onc), respectively. High-volume centers achieved insignificantly higher accuracy scores with regard to the histopathology. Small branch-duct IPMN with cysts <2 cm and malignant potential were not identified by the guideline algorithms. CONCLUSION: The survey underlines the complexity of treatment decisions for patients with PCL; less than 40% of the recommendations were in line with the final histopathology in this selected case panel. Experts and consensus guidelines may fail to predict malignant potential in small PCL.

[Current biomarkers for gastric cancer]. / Aktuelle Biomarker beim Magenkarzinom.

Gastric cancer is still a relevant malignant disease with high morbidity and mortality. Current molecular genetic data show that gastric cancer, as other solid tumors as well, is not a single entity but consists of several molecular subtypes of gastric cancer with diverse biology. The increasing understanding of molecular pathways is the basis for innovative therapies. These either directly target altered signaling pathways or genes in tumor cells or as in immune checkpoint inhibitors, indirectly target tumor cells by blocking tumor-induced immune inhibition leading to improvement in the prognosis. The selection of eligible patients is a prerequisite for the successful clinical application of these targeted drugs. Pathologists play an important role in integrating tissue-based biomarkers and established pathological parameters (typing, grading and staging) into one comprehensive morphomolecular report.

[Histological diagnosis and complications of celiac disease. Update according to the new S2k guidelines]. / Histologische Diagnostik und Komplikationen der Zöliakie. Aktualisierung entsprechend der neuen S2k-Leitlinie.

Celiac disease is a relatively common immunological systemic disease triggered by the protein gluten in genetically predisposed individuals. Classical symptoms like chronic diarrhea, steatorrhea, weight loss and growth retardation are nowadays relatively uncommon. Diagnostic workup includes serological tests for IgA antibodies against tissue transglutaminase 2 (anti-TG2-IgA) and total IgA and histology of duodenal biopsies. Histomorphological classification should be done according to the modified Marsh-Oberhuber classification. Diagnosis of celiac disease should be based on serological, clinical, and histological findings. The only treatment is a life-long gluten-free diet. Unchanged or recurrent symptoms under gluten-free diet may indicate refractory celiac disease. Enteropathy-associated T-cell lymphoma and adenocarcinomas of the small intestine are known complications of celiac disease.

[Intraductal papillary mucinous neoplasm of the pancreas (IPMN)--standards and new aspects]. / Intraduktale papillär-muzinöse Neoplasien (IPMN) des Pankreas--Standards und neue Aspekte.

Intraductal papillary mucinous neoplasms (IPMN) of the pancreas belong to the heterogeneous group of cystic pancreatic lesions and have been diagnosed more frequently in recent years. Diagnosis and differentiation from other cystic lesions (pseudocysts, serous-cystic neoplasias [SCN], mucinous-cystic neoplasias [MCN], intraductal papillary-mucinous neoplasias [IPMN] and solid pseudopapillary neoplasias [SPN]) is often challenging. IPMN of the pancreas are considered as precursor lesions for the development of invasive pancreatic cancer. However, depending on the morphological (MD-IPMN, BD-IPMN) and histological subtype (intestinal, pancreatobiliary, oncocytic or gastric) the malignant potential of IPMNs varies significantly. Hence, early diagnosis and selection of the appropriate therapeutic strategy is necessary for optimal outcome and cure. There is a strong consensus for the resection of all MD-IPMN. Small BD-IPMN without signs of malignancy can be followed by observation. The increasing understanding of the histopathology and tumour biology of IPMN has led to an amendment of the 2006 International Association of Pancreatology (IAP) guidelines for the treatment of cystic pancreatic tumours. In consideration of recent data, recommendations for observation and/or follow-up of IPMN cannot be given definitely.

[Microscopic colitis--new insights relevant to clinical practice]. / Mikroskopische Kolitis--neue praxisrelevante Erkenntnisse.

Microscopic colitis is an increasingly recognised chronic inflammatory bowel disease associated with watery, non-bloody diarrhoea. In addition, many patients suffer from abdominal pain, nocturnal diarrhoea, urgency and incontinence. The two traditional histological subtypes are collagenous colitis and lymphocytic colitis. A novel third subgroup is the so-called incomplete microscopic colitis which is clinically indistinguishable. At present, budesonide is the only evidenced-based effective therapy, however many problems in the long-term treatment strategy are still unsolved. The present paper reviews new developments in microscopic colitis which are relevant for clinical practice.

What can molecular pathology offer for optimal decision making?

In recent years, colorectal cancer (CRC), once a uniform disease with well-understood carcinogenesis, has been divided into at least five different subgroups with distinct precursor lesions, pathways of carcinogenesis, morphological, and molecular characteristics. Moreover, new therapeutic concepts with 'targeted' substances have added to the complexity of the management of CRC patients. The clinical value of biomarkers in advanced CRC is indisputable ever since activating mutations of the KRAS oncogene have been shown to predict resistance to anti-epidermal growth factor receptor antibodies. Prognostic biomarkers predicting patient outcomes and predictive biomarkers forecasting response to a certain therapy may help us to improve therapeutic agent selection and patient management with the ultimate goal of maximizing the benefit of treatment and minimizing toxicity. Biomarkers with known implications in advanced CRC will be discussed in this paper.

New strategies and designs in pancreatic cancer research: consensus guidelines report from a European expert panel.

Although the treatment of pancreatic ductal adenocarcinoma (PDAC) remains a huge challenge, it is entering a new era with the development of new strategies and trial designs. Because there is an increasing number of novel therapeutic agents and potential combinations available to test in patients with PDAC, the identification of robust prognostic and predictive markers and of new targets and relevant pathways is a top priority as well as the design of adequate trials incorporating molecular-driven hypothesis. We presently report a consensus strategy for research in pancreatic cancer that was developed by a multidisciplinary panel of experts from different European institutions and collaborative groups involved in pancreatic cancer. The expert panel embraces the concept of exploratory early proof of concept studies, based on the prediction of response to novel agents and combinations, and randomised phase II studies permitting the selection of the best therapeutic approach to go forward into phase III, where the recommended primary end point remains overall survival. Trials should contain as many translational components as possible, relying on standardised tissue and blood processing and robust biobanking, and including dynamic imaging. Attention should not only be paid to the pancreatic cancer cells but also to microenvironmental factors and stem/stellate cells.

[Histopathology of microscopic colitis]. / Histopathologie der mikroskopischen Kolitis.

Microscopic colitis (MC) is recognized to be a common cause of chronic, non-bloody diarrhea with rising incidence in the last decade. The diagnosis can only be made by histology and the specific histological findings define two subtypes of MC: lymphocytic (LC) or collagenous colitis (CC). The key histological feature of LC is an increased number of surface intraepithelial lymphocytes (IEL). In the literature, >20 IELs/100 epithelial cells are required to warrant the diagnosis of LC. IELs are mostly cytotoxic CD8+ T-lymphocytes. The key histological criterion for CC is a continuous subepithelial fibrous band underneath the surface epithelium (>10 µm). Other hallmarks of CC are chronic mucosal inflammation, and the collagen band can contain entrapped capillaries, red blood cells, and inflammatory cells. Damaged epithelial cells appear flattened, mucin depleted, and irregularly oriented. Focally, small strips of surface epithelium may lift off from their basement membrane. In both subtypes of MC, the lamina propria shows increased numbers of plasma cells and lymphocytes with loss of the normal gradient, even eosinophilic and neutrophilic granulocytes may be present. But these histological features alone do not warrant the diagnosis of MC even though they may be responsible for the clinical symptoms. The term MCi (MC incomplete) is suggested for the subgroup of patients with diarrhea and an increase in cellular infiltrate in the colonic lamina propria and either an abnormal collagenous layer and/or intraepithelial lymphocytes coming but not fulfilling the criteria for CC or LC.

[Barrett's esophagus. An update]. / Barrett-Ösophagus. Aktueller Stand.

Barrett's esophagus (BE), a well-known complication of gastroesophageal reflux disease (GERD), constitutes a precancerous condition for adenocarcinoma of the distal esophagus. The so-called Barrett's carcinoma shows increasing incidences in countries of the western hemisphere; new data, however, indicate that the rise in incidence is not quite as dramatic as previously assumed. The definition of BE is currently changing: despite good reasons for a purely endoscopic definition of BE, goblet cells are still mandatory for this diagnosis in Germany and the USA. Dysplastic changes in the epithelium are the most important risk factor for the development of Barrett's adenocarcinoma and recently dysplasia was subclassified into a more frequent adenomatous (intestinal) and a non-adenomatous (gastric-foveolar) types. The gold standard for diagnosing dysplasia is still H&E staining. The histological diagnosis of dysplasia is still encumbered by a significant interobserver variability, especially regarding the differentiation between low grade dysplasia and inflammatory/reactive changes and the discrimination between high grade dysplasia and adenocarcinoma. Current data, however, show much higher interobserver agreement in endoscopic resection specimens than in biopsies. Nevertheless, the histological diagnosis of dysplasia should be corroborated by an external second opinion because of its clinical consequences. In endoscopic resections of early Barrett's adenocarcinoma, the pathological report has to include a risk stratification for the likelihood of lymphogenic metastases.

Probe-based confocal laser endomicroscopy in double balloon enteroscopy.

BACKGROUND: Probe-based confocal laser endomicroscopy (pCLE) allows in-vivo assessment of the gastrointestinal mucosal architecture during ongoing endoscopy. We investigated the feasibility and safety of pCLE during double balloon enteroscopy (DBE). METHODS: DBE was performed using the Fujinon EN-450P5. pCLE (Cellvizio-GI®, Mauna Kea Technologies) was performed after intravenous injection of 5-10  mL fluorescein 1 % using a 1.8-mm probe (GastroFlex/ColoFlex Z-probe) at the deepest point of DBE insertion and in case of any pathological lesion. Primary outcome measure was technical success, defined as (i) successful advancement of the probe at the deepest DBE insertion and (ii) successful pCLE imaging of the intestinal mucosa. Secondary outcome was safety of the pCLE procedure. RESULTS: 27 DBE procedures (14 antegrade) were performed in 16 patients. The mean depth of small bowel insertion was 255  cm for antegrade and 130  cm for retrograde DBE. Technical success of pCLE was achieved in 96.3 % (antegrade 92.8 %, retrograde 100 %). One technical failure occurred (incomplete probe advancement). There were no adverse events related to the pCLE procedure. pCLE imaging of the small bowel mucosal architecture was possible in all cases. Pathological conditions within the small bowel such as loss of villi, crypt hyperplasia, advanced neoplasia, or increased blood flow due to inflammation tissue could be successful visualized. CONCLUSION: This study is the first to demonstrate successful and safe application of pCLE in the deep small bowel during double balloon enteroscopy. Further studies are needed to determine the clinical benefit of pCLE in the management of patients with small bowel diseases.

[WHO classification 2010 for the lower gastrointestinal tract: what is new?]. / WHO-Klassifikation 2010 für den unteren Gastrointestinaltrakt: Was ist neu?

The new WHO classification of tumors of the digestive system not only redefines common diagnostic terms, such as intraepithelial neoplasia and dysplasia but also introduces changes in the nomenclature and diagnostics of colorectal tumors which will be important in daily practice. Changes in nomenclature and classification include the introduction of serrated adenocarcinoma, cribriform comedo type adenocarcinoma and micropapillary adenocarcinoma as new distinct histological subtypes of colorectal cancer. The grading of mucinous and signet ring carcinomas, which were previously invariably graded as G3/high grade, is now dependent on the microsatellite instability (MSI) status as a high MSI (MSI-H) indicates a better and low or no MSI (MSI-L/MSS) a worse prognosis. Thus, analysis of microsatellite instability via immunohistochemistry or fragment length analysis must be included in the pathological report of these tumors. Serrated polyps/adenomas and their potential of progression into colorectal cancer via the alternative pathway of colorectal carcinogenesis will be discussed as well as new insights into prognostic and predictive markers of colorectal cancer. This manuscript will give an overview of the most important changes within the new WHO classification of colorectal tumors.

[Polyps of the colorectum: non-neoplastic and non-hamartomatous]. / Polypen im Kolorektum: Nichtneoplastisch und nichthamartomatös.

Non-neoplastic and non-hamartomatous colorectal polyps or tumor-like lesions comprise a very heterogeneous group of changes in the colorectal mucosa or the colon wall. Mucosal prolapse-associated lesions and inflammatory polyps, which are predominantly associated with chronic inflammatory bowel disease, are the most prominent examples for polypoid lesions difficult to distinguish from neoplastic lesions such as adenomas, hyperplastic/serrated polyps/adenomas and invasive carcinomas. The considerably less frequent tumor-like lesions like heterotopias, endometriosis, amyloid tumors and pseudolipomatous changes are histologically often well defined and should be considered in the differential diagnosis of colorectal lesions. The etiology, endoscopic and histological appearance of these entities and their most important differential diagnoses are discussed.

[Bacterial colitis]. / Bakterielle Kolitiden.

The question of whether there are inflammatory changes in colorectal biopsy specimens is frequently asked, especially when the patient reports diarrhea or when the mucosa is reddened on endoscopy. The pathologist first has to find out whether there is, in fact, an increase in the inflammatory infiltrate of the colorectal mucosa which warrants the diagnosis of inflammation. If so, the second challenge is to ascertain the etiology of these inflammatory changes, in particular to differentiate between infectious and non-infectious causes. In principle, we can distinguish forms of colitis with distinct morphological hallmarks confirming the diagnosis (e.g. microscopic detection of the causative organism, as well as lymphocytic or collagenous colitis) from other forms of colitis which have a characteristic pattern of findings not necessarily allowing to deduce the etiology (e.g. infectious colitis without microscopic evidence of the germ vs. inflammatory bowel disease). The present article discusses the pathomorphology and differential diagnosis of the most important forms of bacterial colitis.

[Nonbacterial colitides]. / Nichtbakterielle Kolitiden.

Aside from bacterial infections, viral, fungal, and parasitic infections are important differential diagnoses in inflammatory disorders of the colorectum. In contrast to bacterial infections, in which the causative organism can hardly ever be detected histologically, in non bacterial infections the germs can often be verified by either histology, immunohistochemistry, or at least by molecular pathology. This manuscript will give an overview of the spectrum of pathogenic germs, the clinical symptoms, and pathological findings of the most important infections.

[Serrated precursor lesions]. / Serratierte Vorläuferläsionen.

The so-called serrated pathway has in recent years been well established as a second route of colorectal carcinogenesis. Sessile serrated polyps, especially sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA) were identified as precursor lesions of this pathway. Activating mutations in either the BRAF (in SSAs) or the KRAS oncogene (in TSAs) have been determined as the initiating molecular alterations, followed by epigenetic methylation of CpG islands in promoter regions of genes which are implicated in cell cycle control or DNA repair. These findings have led to a paradigm shift in gastrointestinal pathology as lesions without cytological dysplasia, such as SSAs and certain forms of hyperplastic polyps, are now accepted to be precancerous lesions. In addition, carcinomas that have developed through the serrated pathway of colorectal carcinogenesis show varying biological behavior relevant for the clinical management of these tumors depending on the molecular aberrations.

[Histopathological diagnosis and differential diagnosis of colorectal serrated polys: findings of a consensus conference of the working group "gastroenterological pathology of the German Society of Pathology"]. / Histopathologische Diagnostik und Differenzialdiagnostik serratierter Polypen im Kolorektum : Ergebnisse einer Konsensuskonferenz der AG "Gastroenterologische Pathologie der DGP"

Until recently, two major types of colorectal epithelial polyps were distinguished: the adenoma and the hyperplastic polyp. While adenomas - because of their cytological atypia - were recognized as precursor lesions for colorectal carcinoma, hyperplastic polyps were perceived as harmless lesions without any potential for malignant progression, mainly because hyperplastic polyps lack cytological atypia. Meanwhile, it is evident that the lesions formerly classified as hyperplastic represent a heterogeneous group of polyps, some of which exhibit a significant risk of neoplastic progression. These lesions show characteristic epigenetic alterations not commonly seen in colorectal adenomas and progress to colorectal carcinoma via the so-called serrated pathway (CIMP pathway). This group of polyps is comprised not only of hyperplastic polyps, but also of sessile serrated adenomas (SSA), traditional serrated adenomas (TSA) and mixed polyps, showing serrated and "classical" adenomatous features. In a consensus conference of the working group of gastroenterological pathology of the German Society of Pathology, standardization of nomenclature and diagnostic criteria as well as recommendations for clinical management of these serrated polyps were formulated and are presented herein.