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

Molecular studies have shown that different genetic pathways are involved in the history of colorectal carcinomas. This suggests that a correlation exists 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 than two-thirds are located in the distal colon. They have the worst prognosis. The second group has a normal diploid pattern and a phenotypic microsatellite instability without allelic losses. These tumours represent 10-15% of all colorectal carcinomas and about 30% of the right-sided tumours. They are associated with a better prognosis. In the future, it would perhaps be better to classify colorectal carcinomas according to their molecular features rather than to their topographical localizations.