Microsatellite Instability Is Common in Colorectal Cancer in Native Nigerians.

Background: Colorectal cancer (CRC) is the fifth most common cancer in Africa, with significant differences in incidence, biology and clinical behavior from other populations.

Materials And Methods: We studied prevalence and clinicopathological features of microsatellite instability (MSI) and young onset CRC in 83 archival samples from the University of Ibadan, Nigeria.

Results: Nigerian cases of CRC were MSI-high in 43% and MSI-high CRC had significantly lower histological heterogeneity than microsatellite-stable CRC (20% vs. 55% respectively, p=0.046). Presence of signet ring cell differentiation (10-50% of tumor) was significantly higher in younger patients with CRC (<50 years) (odds ratio(OR)=5.93, 95% confidence interval(CI)=1.17-29.95, p=0.038). Poor differentiation (34%), invasive growth (96%), and high prevalence of mucinous (10%) and signet ring cell adenocarcinomas (4%) were among distinct features of Nigerian patients with CRC.

Conclusion: MSI-high CRC is more common in West Africa and more detailed molecular and genetic analysis is warranted as CRC incidence and mortality continue to increase in the Sub-Saharan Africa.