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 per cent of all cases of large bowel malignancy. The male:female ratio was 2.28:1. Most of the cases (65.9%) were below 50 years 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 per cent each. Seventy-three per cent of the tumours were well differentiated adenocarcinoma while 15.9 per cent were poorly differentiated. Mucinous carcinoma and signet ring carcinoma were found in 7.3 per cent and 3.7 per cent respectively. There were colonic metastasis in 54.9 per cent of cases and 20.8 per cent had distant metastasis at initial surgery. Associated lesions were villous adenoma, 24.4 per cent tubular adenoma 17.1 percent, amoebiasis 6.1 per cent and Schistosomiasis 3.7 per cent. The above observations together with those of previous authors suggest a difference in the biology of colorectal carcinomas in the tropics. The association with chronic granulomatous diseases, in particular, may be indicative of entirely different oncogenic mechanisms in their development in the tropics.