Are there several types of colorectal carcinomas? Correlations with genetic data

Molecular studies have shown that different genetic pathways are involved i n the history of colorectal carcinomas. This suggests that a correlation ex ists between the molecular, clinical and pathological features of tumours. Two large groups can be individualized: the first group is characterized by allelic losses and hyperdiploidy. These LOH (for loss of heterozygosity) - positive tumours represent 80% of colorectal carcinomas. Among them more th an two-thirds are located in the distal colon. They have the worst prognosi s. The second group has a normal diploid pattern and a phenotypic microsate llite instability without allelic losses. These tumours represent 10-15% of all colorectal carcinomas and about 30% of the right-sided tumours. They a re associated with a better prognosis. In the future, it would perhaps be b etter to classify colorectal carcinomas according to their molecular featur es rather than to their topographical localizations. (C) 1999 Lippincott Wi lliams & Wilkins.