Expression of cyclooxygenase-2 (COX-2) in colorectal adenoma in an indigenous African population in northern Nigeria.

Background: The clinical significance of adenoma is as a result of being a precancerous lesion with long latency, harbouring of invasive carcinoma, bearing similar clinical features with colorectal cancer, and as part of hereditary colorectal cancer syndromes. Over-expression of the cyclooxygenase-2 (COX-2) enzyme has been noticed in adenomas with unfavourable features. However, this information is limited in Africa.

Objective: This study aimed to assess the proportion of adenomas in northern Nigeria that over-express COX-2.

Methods: This 5-year retrospective, descriptive, hospital-based study examined the COX-2 immunohistochemistry of all histologically diagnosed colorectal adenomas in Aminu Kano Teaching Hospital, Kano, Nigeria, between 01 January 2015 and 31 December 2019. Age, sex, site, diagnosis, and grade were obtained from the Kano cancer registry and slide reviews of cases.

Results: There were cases of 29 adenoma (male, n = 20; female, n = 9). Adenoma occurred more commonly among male patients (M:F, 2.2:1), in the age group 40-79 years, and included tubular adenomas (62.1%), tubulovillous adenomas (27.6%), and villous adenomas (10.3%). Over-expression of COX-2 was observed in 3.4%. There was no association between COX-2 expression and age, sex, site, histological subtype, or grade.

Conclusion: Over-expressed COX-2 was observed in only 3.4% of adenomas, which may indicate its early involvement in the spectrum of adenoma-carcinoma sequence.

What this study adds: It provides key information about COX-2 expression in adenoma in an African population, which may serve as a rationale for other studies regarding COX-2 targets for chemoprevention and therapy in adenoma and colorectal cancer.