Introduction: It has been reported that HNPCC colorectal carcinomas demonstrate a better prognosis compared to sporadic carcinoma, however the exact mechanism for this is still uncertain. It is possible that tumour morphology, location and cell cycle markers may be indicators of the underlying molecular mechanism. In a resource limited setting these factors may help to stratify which cases need further molecular testing and genetic counselling. Aims and objectives: To characterise the macroscopic and microscopic pathology in three cohorts of patients. The cohorts include (1) patients with CRCs that are < 50 years and mutation negative, (2) < 50 years and DNA mismatch repair gene mutation positive and (3) more than 50 years (sporadic). To investigate the immunoexpression of the cell cycle regulators (p21, p27, p53, c-myc, cyclin D1 and cyclin E) and MMP-7 in each cohort. To compare the immunoexpression of each marker between cohort s. To correlate the immunoexpression of each marker with tumour type, stage and grade. Materials and methods: In total, 17 mutation negative, 15 mutation positive and 28 sporadic adenocarcinoma resection cases were available for study. The histopathological features of all cases were reviewed. The cases were stained with antibodies against p21, p27, cyclin D1, cyclin E, p53, c- myc MMP -7, MLH1, MSH2 and MSH6. Results were considered statistically significant if P < 0.05, and P <0.017 if 3 pairs of medians were compared. Results: The mutation positive tumours were more frequently right sided tumours and showed mucinous differentiation, tumour infiltrating lymphocytes and an expanding border. The sporadic and mutation negative cohort s showed similar morphology. In the sporadic cohort, the five tumours that were MLH1 negative demonstrated morphological features of MSI-H tumours. MLH1 mutations were the commonest. MLH1 immuno expression was lost in the mutation positive tumours and was statistically significant when compared to the other two cohorts. There was no statistical significance among the three cohorts for MSH2 and MSH6 immunoexpression. There was no statistically significant difference in immunoexpression for p21, p27, p53 and MMP-7 among the three cohorts. Furthermore, there was no association with tumour type and stage. Cyclin D1 expression was increased in the mutation positive cohort and was statistically significant when compared to the mutation negative cohort only. Cyclin E expression was also increased in the mutation positive cohort and was statistically significant when compared to the sporadic cohort only. Conclusion: The morphological features of colorectal carcinomas can be helpful in identifying MS I-H tumours and cases requiring further molecular studies. The cell cycle marker expression s did not explain the expected differences in patient outcome and prognosis. The mutation negative cohort in our population continues to remain enigmatic and further testing at the molecular level is required, that may reveal another novel pathway of colorectal carcinogenesis or other novel mutations in mismatch repair genes.

Includes bibliographical references (leaves 52-65). / Gastric remnant carcinoma (GRC) is a gastric cancer that develops in gastric remnant more than five years after resection for benign disease. GRC comprises 1 %-9% of all gastric cancers. Partial gastrectomy for peptic ulcer is thought to be a risk factor for GRC. Pancreato-duodenal and bile reflux may play an important part in the aetiology of GRC. Primary gastric carcinoma (pGC) is a gastric cancer that arises in un-operated stomach and chronic gastritis is a well-known risk factor. Consequently there appear to be differences in the aetiology of GRC and PGC. According to many studies, surgical treatment of early GRC (Stage I or II) resulted in the same or better prognosis with similar stage PGC. However if diagnosed late, GRC has a worse prognosis than PGC at the same stage. In this study haematoxylin and eosin, alcian blue pH 2.5, periodic acid Schiff, high iron diamine and Giemsa stains as well as immunohistochemical methods (eight antibodies against MUCI to MUC6) were used to determine the type of mucin and the pattern of staining in twenty cases of GRC and twenty PGC (ten cases of intestinal type PGC, ten diffuse type PGC) and ten normal gastric mucosal biopsies. The aim of the study was to describe the morphology of GRC and the adjacent gastric mucosa, as well as to determine the histochemical and immunohistochemical mucin profile of GRC and to compare this with that of PGC and normal mucosa.

Includes abstract. / Includes bibliographical references (leaves 80-93). / The study aimed to contribute a South African perspective by correlating the HIV status and prognosis of DLBCL and PBL with differentiation profiles assessed by immunophenotyping.

Includes bibliographical references (leaves 163-176). / The term "Nonalcoholic steatohepatitis" (NASH) describes a form of liver disease indistinguishable from alcoholic liver disease, but present in persons who consume insignificant amounts of alcohol. The spectrum of non-alcoholic liver disease ranges from non-progressive steatosis, through to NASH and sometimes to cirrhosis. Risk factors predisposing to NASH include obesity, diabetes mellitus, hypertriglyceridermia and procedures leading to rapid and profound weight loss such as gastric bypass and bulimia. Given the high incidence of type II diabetes, obesity and various types of hyperlipidaemia in the Western Cape, NASH has become one of the most commonly encountered liver diseases in the Liver Clinic, Groote Schuur Hospital. Statistics also suggest nonalcoholic fatty liver disease underlies most cases of elevated liver enzymes in many other parts of the world. The exact pathogenic mechanisms involved are not well understood, and no effective treatment options are currently available. However, animal models of NASH now provide unique opportunities for study of this disease in the laboratory setting. This thesis employs a dietary animal model, which restricts methionine and choline intake, to replicate aspects of the injurious process in human NASH. Two lines of inquiry are pursued. The first involves an assessment of the effect of alcohol consumption on fatty liver of non- alcoholic aetiology. Elevated liver enzymes, altered levels of lipid peroxides, and increased cytochrome P450 activity recorded in this study, suggest alcohol may exacerbate nonalcoholic fatty liver disease. The second line of inquiry is an exploration of the role of Tumor Necrosis Factor alpha (TNFα, a cytokine implicated in pathogenesis of alcoholic liver disease and thought to be pivotal in NASH pathogenesis. The role of TNFα in the dietary model of NASH is investigated using mice lacking functional TNFα genes, as well as wild type mice in which expression of this cytokine is induced by endotoxin challenge. Endotoxin challenge does elicit a marked inflammatory response and enhanced generation of lipid peroxides in the fatty liver, both of which may contribute to injury. However, as knockout mice still develop experimental NASH, TNFα cannot be considered the sole driving force required for the development of NASH. This strength of the project lies in the use of a variety of techniques (in the fields of Pathology, Immunology and Lipid Biochemistry) to investigate a range of aspects of NASH. The results of the alcohol study may provide the first empirical evidence supporting the need to restrict alcohol intake in patients with NASH, while the data on TNFα is vital for illuminating the complex, (potentially) counter-intuitive role of this cytokine in NASH. Where definitive conclusions cannot be drawn from the data, the questions posited may constitute the basis for future research.

Nine human mucin genes have been described, which express glycoproteins MUCJ,2,3,4 ,5AC,5B,6, 7, and 8 in various tissues. It has been shown that different mucins are expressed in various gastric disease states as compared to the normal. In this study histochemical and immunohistochemical methods were used to determine the type of mucin and the pattern of staining in 54 patients with a variety of gastric conditions [i.e. normal controls, foetal stomachs, chronic active gastritis, low grade dysplasia, intestinal metaplasia (associated with gastritis, benign ulcers, dysplasia and cancer), early and advanced intestinal type adenocarcinoma, and diffuse adenocarcinoma]. MUCJ-7 antibodies were used in the study, this being the first study to all assess seven MUC antibodies in the various conditions. It is also the first study to assess the pattern of mucin staining in foetal stomachs. Normal controls were immunoreactive for MUC4, 5 and 6, and gastritis specimens showed similar results, although the latter showed more MUCJ immunoreactivity. Whereas early foetal stomach showed no MUC immunoreactivity, MUC4, 5 and 6 were present from the early second trimester onwards. There was no significant difference between dysplasia and intestinal metaplasia, both categories showing expression of MUC2 and 3 predominantly. Early intestinal type adenocarcinomas did not show any mucins in the majority of cases. Advanced intestinal type adenocarcinomas showed immunoreactivity predominantly for MUCJ, 5 and 6, as well as MUC2 in some cases. Diffuse adenocarcinomas showed strong positive MUC2 and MUC6 staining, and in some cases MUC5 and 7. In conclusion this study has shown different patterns of mucin immunoreactivity in various gastric disease states. Specimens with dysplasia, intestinal metaplasia, late intestinal type adenocarcinoma and diffuse gastric cancer were characterized by increased diversity of mucin gene expression, whereas early intestinal cancer showed loss of mucin immunoreactivity.

Includes bibliographical references. / Arrhythmogenic right ventricular cardiomyopathy / dysplasia (ARVC/D) is a genetic disease causing fibro-fatty replacement of the right ventricular myocardium, resulting in cardiac arrhythmias and sudden death. Part of the diagnostic work up for these patients includes a biopsy of the endocardium which has historically been difficult to interpret and of limited value in the early stages of disease. This study will focus on novel immunohistochemical stains of the cardiac desmosomes. These will be used to try to aid in the early diagnosis of ARVC.

Objective: Thyroid cancer affects approximately 298 million people worldwide and the major challenge is reliably distinguishing patients who present with poor prognosis from those who do not. There are genetic markers that have been shown to be associated with poor clinical outcome in thyroid cancer, which include mutations in the BRAF and RAS genes. In addition to genetic variation, recent studies have reported on the effects of micro-ribonucleic acids' (miRNAs) differential expression observed in tumour and normal tissue as another possible marker of thyroid cancer prognosis. Therefore, miRNA expression signatures in thyroid cancer could be used as biomarkers for prognosis and diagnosis. This study compared the expression of miRNAs in papillary thyroid cancer and follicular thyroid cancer. Methods: As part of a preliminary study, 66 differentiated thyroid cancer samples were obtained from patients attending Groote Schuur Hospital and used in the study. MiRNA miScript polymerase chain reaction (PCR) Array (Qiagen) was used to determine the differential miRNA expression profiles between follicular thyroid carcinoma (FTC) and papillary thyroid carcinoma (PTC). Real time PCR was employed to confirm the expression levels of miRNA- 21 and miRNA-122. Results: 17 miRNAs were upregulated in PTC and 14 in FTC. There were significant differences in the miRNA expression between FTC and PTC. For example, miRNA-21 was the most upregulated miRNA in PTC and miRNA-122 in FTC. We found no correlation of the expression of these miRNAs to clinicopathological features. We observed an association of BRAF mutation positivity to advanced tumour stage and advanced age of presentation however, no correlation was seen to miRNA-21 or miRNA-122 expression. Conclusion: Although we did not observe correlations between miRNAs and any of the clinicopathological features, microRNA expression profile signatures were able to differentiate between PTC and FTC and could potentially be further validated as diagnostic markers.

Includes bibliographical references (leaves 64-71). / Cyclin E and p27 expression is easy to assess in human tissues by standard immunohistochemical techniques. Immunohistochemistry is cost effective, relatively easy to perform and will play more of a role in the future management of cancer. To investigate the role of p27 and cyclin E immunoexpression as a prognostic factor in early breast carcinoma. Cyclin E and p27 immunohistochemistry was performed on sixty six cases of breast carcinoma submtted over a five year period to the Division of Anatomical Pathology, Groote Schuur hospital; Whittaker and Associates; and PathCare. All tumours included in this study were less than 5cm in diameter (pT1 and pT2 stage) and all the patients had wide local excisions peformed. Follow up information was obtained from patient folders in the Department of Radiation Oncology.

Includes bibliographical references. / Fatty liver disease is a collective phrase for a spectrum of diseases characterised by increased liver fat content. It ranges from fatty infiltration of the liver to an inflammatory condition, steatohepatitis, which may lead onto cirrhosis. Although not associated with alcohol consumption, non-alcoholic steatohepatitis (NASH) has strong associations with obesity, diabetes and dyslipidaemia. Overlapping pathological mechanisms may be involved. The course of the disease will remain unpredictable, and specific treatment will only be able to be instituted once the pathogenesis is fully understood. This thesis reviews current understanding of the pathogenesis and explores the suitability of a recently defined obese diabetic mouse model for its value as a model in the heterozygous and homozygous states. Observations revealed that the db/wt phenotype has a larger mass than the wt/wt and responds with hyperglycaemia. Lipid accumulation occurs in this model when alcohol is administered and lipid peroxidation occurs but histological changes of steatosis and steatohepatitis do not occur. The db/db model is phenotypically distinguished by a large amount of fat storage, diabetes and macrovesicular steatosis that has more lipid peroxidation but no steatohepatitis even when alcohol further increases lipid peroxidation. The model, as explored, did not reveal steatohepatitis either alone, or with alcohol as a single additional stressor, but both the db/wt and db/db mouse model could be further investigated to explore whether additional stressors could induce steaotohepatitis in this model.

Includes abstract. / Includes bibliographical references. / The WNT pathway is a major developmental pathway that plays an important role in the development of many tumours, including neuroectodermal and bone tumours. Ewing sarcoma (ES) / primitive neuroectodermal tumour (PNET) shows varying degrees of neuroectodermal differentiation and is the second commonest bone malignancy in childhood. A recent study on ES cell lines using RT-PCR analysis and biological response assays suggests that an intact WNT pathway exists in ES and that addition of exogenous WNT ligands enhances cell motility. Based on this we hypothesize that the WNT pathway may play a role in the biology of ES/PNET and we aim to investigate this by immunohistochemical stains on archival tissue.