Kisha A. Mitchell

Diagnostic importance of 9p21 homozygous deletion in malignant mesotheliomas

Definitive diagnosis of malignant mesothelioma in small specimens can be extremely difficult based on morphology alone. Homozygous deletion of 9p21, the locus harboring the p16 gene, has been reported as the most common genetic alteration in malignant mesotheliomas. Recent studies demonstrated that this alteration may be useful for differentiating benign from malignant mesothelial proliferations in cytology specimens. The aim of this study was to evaluate the diagnostic utility of homozygous deletion of 9p21 assessed by fluorescence in situ hybridization (FISH) in mesothelial proliferations involving serosal surfaces in paraffin-embedded tissue. p16 protein immunoexpression was also explored as a potential diagnostic aid. FISH analysis demonstrated homozygous deletion of the 9p21 locus in 35 of 52 cases (67%) of pleural mesothelioma and in 5 of 20 cases of peritoneal mesothelioma (25%) (P<0.005). None of 40 cases of reactive pleural mesothelial proliferations showed p16 deletion (P<0.005). Loss of immunoexpression of p16 was observed in 71% of the peritoneal mesotheliomas, 40% of the pleural malignant mesotheliomas and 15% of the reactive mesothelial cells. Homozygous deletion did not correlate with p16 protein expression in any of the studied groups. Our study suggests that 9p21 homozygous deletion assessed by FISH on paraffin-embedded tissue may be helpful for differentiating between malignant mesotheliomas and reactive mesothelial proliferations. A discrepancy between p16 protein expression and homozygous deletion suggests that other molecular mechanisms may play a role in p16 protein expression in mesothelial proliferations.

The Role of the Carbohydrate Response Element-Binding Protein in Male Fructose-Fed Rats

By 2030, nearly half of Americans will have nonalcoholic fatty liver disease. In part, this epidemic is fueled by the increasing consumption of caloric sweeteners coupled with an innate capacity to convert sugar into fat via hepatic de novo lipogenesis. In addition to serving as substrates, monosaccharides also increase the expression of key enzymes involved in de novo lipogenesis via the carbohydrate response element-binding protein (ChREBP). To determine whether ChREBP is a potential therapeutic target, we decreased hepatic expression of ChREBP with a specific antisense oligonucleotide (ASO) in male Sprague-Dawley rats fed either a high-fructose or high-fat diet. ChREBP ASO treatment decreased plasma triglyceride concentrations compared with control ASO treatment in both diet groups. The reduction was more pronounced in the fructose-fed group and attributed to decreased hepatic expression of ACC2, FAS, SCD1, and MTTP and a decrease in the rate of hepatic triglyceride secretion. This was associated with an increase in insulin-stimulated peripheral glucose uptake, as assessed by the hyperinsulinemic-euglycemic clamp. In contrast, ChREBP ASO did not alter hepatic lipid content or hepatic insulin sensitivity. Interestingly, fructose-fed rats treated with ChREBP ASO had increased plasma uric acid, alanine transaminase, and aspartate aminotransferase concentrations. This was associated with decreased expression of fructose aldolase and fructokinase, reminiscent of inherited disorders of fructose metabolism. In summary, these studies suggest that targeting ChREBP may prevent fructose-induced hypertriglyceridemia but without the improvements in hepatic steatosis and hepatic insulin responsiveness.

Ipilimumab-induced perforating colitis.

Recently, a monoclonal antibody to cytotoxic T-lymphocyte-associated antigen 4, ipilimumab, was approved for the treatment of metastatic melanoma. One of the most common side effects associated with this therapy is diarrhea and colitis. We report 3 cases of perforating colitis induced by ipilimumab requiring colectomy. The histologic findings of mucosal biopsies have been previously described. Herein, we describe novel associated histologic findings (pseudopolyp formation, fissuring ulcers, dilated crypts, and lack of intraepithelial lymphocytosis and epithelial apoptosis) of segmental resections in patients who required subtotal colectomy after perforation due to the severity of their ipilimumab-induced colitis. Although steroid therapy is the standard treatment for ipilimumab-induced colitis, surgery may be necessary. In the setting of progressive or worsening diarrhea after steroid therapy in patients with colitis, bowel perforation should be considered.

Pathology of the liver in copper overload.

Copper accumulation in the liver is associated with cellular and apoptotic injury. Wilson disease is the most well-characterized disorder of disordered copper metabolism. Other less-common disorders include Indian childhood cirrhosis, endemic Tyrolean infantile cirrhosis, and idiopathic copper toxicosis. The histopathologic spectrum of the liver in Wilson disease is extremely variable and overlaps among the different entities, though this review will focus on the pathology of Wilson disease. The findings lack specificity, although characteristic findings are observed. Unlike other disorders of copper overload, the pathologic changes are typically sequential, ranging from little or no significant findings to cirrhosis with or without widespread hepatocellular damage. Steatosis and glycogenated nuclei are frequent. Staining of copper is an unreliable method of diagnosis of Wilson disease, whether there are minimal histologic abnormalities or chronic liver disease. Copper and copper-associated protein accumulation may also be seen in chronic biliary obstructive processes.

Appropriate use of special stains for identifying helicobacter pylori: Recommendations from the Rodger C. Haggitt gastrointestinal pathology society

Helicobacter pylori is a major cause of gastroduodenal injury, gastric cancer, and lymphoma, and, thus, there is great interest in its detection and eradication. Several detection methods are available, including histochemical and immunohistochemical stains. Application of these stains in clinical practice is heterogenous, to say the least. Although they were developed to enhance H. pylori detection, changing practice models, financial considerations, and a perceived need for rapid case turnaround have led to their widespread use in routine staining studies ordered reflexively on all gastric biopsies. Emerging data suggest that most of these stains are not needed to establish a diagnosis of H. pylori infection, and their added value when biopsies show minimal, or no, inflammation is not clear. In this manuscript, the Rodger C. Haggitt Gastrointestinal Pathology Society puts forth recommendations regarding ancillary stain usage for H. pylori detection based upon critical literature review and collective experience. Pathologists rarely, if ever, detect H. pylori in “normal” biopsies, but readily observe them in optimally stained hematoxylin and eosin sections from infected patients. Therefore, we suggest that use of ancillary stains is appropriate when biopsies show chronic, or chronic active, gastritis without detectable H. pylori in hematoxylin and eosin-stained sections, but performing them “up front” on all gastric biopsies is generally unnecessary. Application of these stains to nongastric biopsies and polyps is appropriate in an extremely limited set of circumstances. It is our hope that recommendations provided herein will provide helpful information to gastroenterologists, pathologists, and others involved in the evaluation of patients for possible H. pylori infection.

Cancer and Leukemia Group B Pathology Committee Guidelines for Tissue Microarray Construction Representing Multicenter Prospective Clinical Trial Tissues

Practice-changing evidence requires confirmation, preferably in multi-institutional clinical trials. The collection of tissue within such trials has enabled biomarker studies and evaluation of companion diagnostic tests. Tissue microarrays (TMAs) have become a standard approach in many cooperative oncology groups. A principal goal is to maximize the number of assays with this precious tissue. However, production strategies for these arrays have not been standardized, possibly decreasing the value of the study. In this article, members of the Cancer and Leukemia Group B Pathology Committee relay our experiences as array facility directors and propose guidelines regarding the production of high-quality TMAs for cooperative group studies. We also discuss statistical issues arising from having a proportion of patients available for TMAs and the possibility that patients with TMAs fail to represent the greater study population.

Regulated traffic of anion transporters in mammalian Brunner's glands: a role for water and fluid transport

The Brunners glands of the proximal duodenum exert barrier functions through secretion of glycoproteins and antimicrobial peptides. However, ion transporter localization, function, and regulation in the glands are less clear. Mapping the subcellular distribution of transporters is an important step toward elucidating trafficking mechanisms of fluid transport in the gland. The present study examined 1) changes in the distribution of intestinal anion transporters and the aquaporin 5 (AQP5) water channel in rat Brunners glands following second messenger activation and 2) anion transporter distribution in Brunners glands from healthy and disease-affected human tissues. Cystic fibrosis transmembrane conductance regulator (CFTR), AQP5, sodium-potassium-coupled chloride cotransporter 1 (NKCC1), sodium-bicarbonate cotransporter (NBCe1), and the proton pump vacuolar ATPase (V-ATPase) were localized to distinct membrane domains and in endosomes at steady state. Carbachol and cAMP redistributed CFTR to the apical membrane. cAMP-dependent recruitment of CFTR to the apical membrane was accompanied by recruitment of AQP5 that was reversed by a PKA inhibitor. cAMP also induced apical trafficking of V-ATPase and redistribution of NKCC1 and NBCe1 to the basolateral membranes. The steady-state distribution of AQP5, CFTR, NBCe1, NKCC1, and V-ATPase in human Brunners glands from healthy controls, cystic fibrosis, and celiac disease resembled that of rat; however, the distribution profiles were markedly attenuated in the disease-affected duodenum. These data support functional transport of chloride, bicarbonate, water, and protons by second messenger-regulated traffic in mammalian Brunners glands under physiological and pathophysiological conditions.

Differences in germinal centre and non-germinal center phenotype in gastric and intestinal diffuse large B-cell lymphomas.

The gastrointestinal tract is the most common extranodal site of lymphoma, and the most common gastrointestinal lymphoma is diffuse large B-cell type (DLBCL). DLBCL can be separated into germinal centre (GCP) and non-germinal centre phenotypes (non-GCP) using CD10, BCL-6 and MUM1 immunohistochemistry, but primary gastrointestinal DLBCL has not been extensively studied. We investigated 48 cases of primary gastrointestinal DLBCL (33% involving the small intestine, 50% the stomach, 13% the large intestine and 4% the ileocecal junction) and found that most (88%) DLBCL in the intestines were of GCP, while only 58% of gastric DLBCL were of GCP. This difference in GCP and non-GCP in gastric vs. intestinal DLBCL may be due to variations in lymphomagenesis reflecting acquired vs. native mucosa-associated lymphoid tissue. There was no significant difference in either overall survival or disease-free survival between the germinal centre and non-germinal centre groups. The distribution of Helicobacter pylori in different gastric DLBCL phenotypes raises interesting questions about the pathogenesis of H. pylori-associated lymphomas.

KRAS mutations are associated with specific morphologic features in colon cancer.

Background: Mutations in the KRAS gene occur at an early stage in the development of colorectal carcinoma. Importantly, KRAS mutation predicts resistance to anti-epidermal growth factor receptor therapy in stage IV disease. Goals: The aim of the current study is to correlate histologic features of colon cancer with the presence of KRAS mutations. Study: Tumor tissue from 145 colon cancer resections was tested for KRAS mutations. KRAS mutation status was correlated with demographic and histologic characteristics. Statistical analysis was performed using the Pearson &khgr;2 test and multivariate analysis. Results: KRAS mutations were present in 55/145 cases (37.9%), consistent with reported rates. KRAS mutations were significantly associated with usual adenocarcinoma morphology (multivariate P=0.014), peritumoral lymphocytic response (&khgr;2, P=0.028; multivariate P=0.017), T3-T4 status (&khgr;2, P=0.012; multivariate P=0.015), right-sided location (multivariate P=0.027), absence of lymphovascular invasion (multivariate P=0.008), and metastases at the time of resection (multivariate P=0.034). No association was found between KRAS mutation status and other factors. Conclusions: Specific morphologic features in colon cancer suggest a higher likelihood of the presence of KRAS mutations. These morphologic features overlap partially with those associated with DNA mismatch repair gene mutations. If confirmed, these results may suggest a paradigm for directed KRAS testing.

Serous cystadenoma in communication with the pancreatic duct: an unusual radiologic and pathologic entity.

Cross-sectional imaging is frequently used in the diagnosis of pancreatic cysts, but there can be overlap in radiographic appearance. We present a case of a patient with presumed intraductal papillary mucinous neoplasm (IPMN) who was ultimately found to have a serous cystadenoma in communication with the pancreatic duct. A literature search for serous cystadenoma communicating with the pancreatic duct was performed and the data was reviewed in the context of this case report. Three reports of patients with serous cystadenoma communicating with the pancreatic duct were identified. Review of current data revealed that endoscopic ultrasound (EUS) has an important role in distinguishing between pancreatic cystic lesions preoperatively. Distinguishing between serous and mucinous cystadenomas and IPMN is essential to guide appropriate management. Although communication with the pancreatic duct is usually pathognomonic of IPMN, rarely this may be a misdiagnosis of a serous cystadenoma and EUS may be necessary for further evaluation. If EUS cannot be performed, resection is favored to avoid undertreating a premalignant lesion.