Colorectal cancer in South Africa: A heritable cause suspected in many young black patients

Abstract

Background:
Colorectal carcinoma (CRC) has a low incidence amongst the black African population. Largely unrecognised in the scientific literature is that a disproportionately large number of young black patients (<50 years old) present with CRC.
Objectives:
To analyse these tumours which we propose may link them to morphological features associated with known genetic pathways.
Methods:
Retrospective review of South African patients histologically diagnosed as CRC in the Division of Anatomical Pathology, National Health Laboratory Service (NHLS) and University of the Witwatersrand (1732 patients, 1990 – 2003). Histology was fully reviewed in 609 patients (1997 – 2002) and all specimens from patients under the age of 50 years were subjected to immunohistochemistry for mismatch repair proteins, as well as APC and p53 proteins.
Results:
Most young patients (<50 years) were black (41% vs 10% white; p ≤ 0.001). Blacks had predominantly proximal tumours, significantly more poorly differentiated and/or mucinous tumours (p = 0.006) and loss of mismatch repair protein expression was more evident than in whites.
Conclusions:
It seems likely that CRC in young blacks develop through the accumulation of mutations, most likely through mismatch repair deficiency or promoter methylation, which in turn is linked to a poor differentiation and a mucinous architecture.