The surgical pathology of colorectal carcinomas in Nigerians.

This paper presents a 10-year experience on the examination of surgical specimens of colorectal carcinomas in Nigerians. Colorectal carcinomas were found to constitute about 80% of all cases of large bowel malignancy. The Male: Female ratio was 2.28:2. Most of the cases (65.9%) were 50 years or younger and the peak incidence was in the 41-50 year age group. The site distribution in order of frequency was recto-sigmoid area (57.3%), descending colon (23.2%), caecum (12.2%) ascending colon and transverse colon 3.7% each. Seventy-three percent of the tumours were well differentiated adenocarcinomas while 15.9% were poorly differentiated. Mucinous carcinoma and signet ring carcinoma were found in 7.3% and 3.7% respectively. There was colonic metastasis in 54.9% of cases and 20.8% had distant metastases at initial surgery. Associated lesions were villous adenoma, 24.4%, Tubular adenoma-17.1%, amoebiasis 6.1% and schistosomiasis, 3.7%. The above observations together with those of previous authors suggests a difference in the biology of colorectal carcinomas in the tropics. The association with chronic granulomatous diseases, in particular, may be indicative of an entirely different oncogenic mechanism in their development in the tropics.