Background: Microsatellite instability (MSI) is a hallmark of DNA mismatch repair defect; and in some populations they have been found to have distinct clinicopathological features, prognostic implications and to be predictive of response to the chemotherapeutic drug cisplatin in gastric carcinoma.
Aim: The aims of this study are to (i) define the rate of MSI in patients with gastric carcinoma from the University College Hospital, Ibadan, (ii) compare the clinicopathological features of MSI and microsatellite stable (MSS) tumours.
Methods: The clinical and demographic data of 47 patients diagnosed between 2000 and 2011 were retrieved from the UCH Cancer Registry, the Pathology Department records and from the UCH Medical Records. Slides were made from archival samples of the same patients and reviewed to confirm the histological diagnoses, subtype the tumour and determine the presence/ absence of other clinicopathological parameters. MSI was assessed on the 47 formalin-fixed, paraffin-embedded gastric carcinoma tissue samples using High Resolution Melt Analysis on BAT 25 and BAT 26 microsatellite loci. Statistical analyses were done using SPSS version 19.
Results: A total of 12 of 47 cases (25.5%) were unstable at either the BAT 25 or BAT 26 loci (BAT 25 = 9/37 cases; BAT 26 = 3/28 cases). No association was found between the clinicopathological features of gastric carcinoma and the microsatellite status.
Conclusions: About a quarter of gastric carcinoma from our cohort is MSI-positive, although no association was found between the microsatellite status of the tumours and the clinicopathological features, probably due to the small sample size used in this study. The implication of this finding is that DNA mismatch repair defect is a pathogenetic mechanism of gastric carcinoma in a significant proportion of our patients. Lastly due the mismatch repair defect this proportion of our gastric carcinoma patients may show poor response to cisplatin-based chemotherapy.