Colorectal carcinoma from Saudi Arabia Analysis of MLH-1, MSH-2 and p53 genes by immunohistochemistry and tissue microarray analysis

To document the incidence and role of p53 and DNA mismatch repair proteins in colorectal carcinomas, and to evaluate the relative frequency of major molecular pathways in colorectal cancers from Saudi Arabia. We collected the formalin fixed, paraffin embedded tissues from 154 colorectal tumors [83 patients from King Faisal Specialist Hospital and Research Centre and 71 from Saudi Aramco Dhahran Health Centre] between January 1989 and December 2003. We analyzed the p53 and mismatch repair gene expression [hMSH-2, hMLH-1] by immunohistochemistry in tissue microarray format. Expression loss of at least one mismatch repair gene was found in 33.8% of cases and significantly associated with the right-sided tumor location [p=0.0047]. The p53 positivity was observed in 57.5% of tumors, and was inversely linked to expression loss of mismatch repair genes [P=0.0102]. The strong confirmation of the previously established associations between tumor phenotype, and mismatch repair gene alteration provided strong evidence for the validity of our experimental approach. Together with the higher incidence of right sided location in Saudi [46.6%] than in Western colon cancers [34.9%], the observed high prevalence of mismatch gene expression loss in Saudi tumors argues for a higher importance of microsatellite instability in this population. If confirmed, it will be interesting to see whether an increased level of familial or sporadic microsatellite instability cases is causing this variation

Ki-1 large cell lymphoma: a clinical study of 12 cases

The treatment and prognosis of Ki-1 positive lymphoma, a relatively new entity, remains largely unknown and the clinical features are still being defined. This is a retrospective analysis of our experience with 12 patients with Ki-1 lymphoma who were treated at our hospital over two years. Clinical presentation and management are described and an attempt is made to identify prognostic factors. The median age at presentation was 20 and the male/female ratio 1:1. Nine patients presented with nodal disease and three with extranodal. B symptoms were present in seven patients. Seven patients had stage I/II disease and five had stage IV. Immunophenotyping was available in 10 patients of which five were T-cell, two B-cell, and two null cell; one could not be categorized. All 12 patients received combination chemotherapy; five had consolidation radiotherapy. With a median follow-up of 11 months [range one to 29], actuarial survival was 67% at 29 months and disease-free survival 50% for all patients. Five out of seven patients with stage I/II and one out of five with stage IV remain disease free. We conclude that the clinical presentation is diverse and advanced stage appears to be the only identifiable adverse prognostic factor