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Abstract
Colorectal cancer is a disease with a major worldwide burden. It is the fourth most frequently diagnosed
malignancy in both sexes, the third most common cause of cancer death in the world, and it is the most
common malignancy of the gastrointestinal tract. The risk of CRC continues to increase with age, and is
higher in men than in women.
A number of factors have been considered important in its causation, and certain clinical conditions are
considered precursors of carcinoma. The initiation stage involves a complex and poorly understood interplay between environmental factors and host
susceptibility. Diet rich in red meat, alcohol intake,obesity, decreased physical activity are all factors
increasing the risk of development of colorectal cancer. Colorectal carcinoma is a genetically heterogeneous disease, and a series of genetic events has been described in the evolution of colorectal
carcinoma. However, the majority of cases of CRC cannot be attributed to known genetic defects even when associated with a family history of CRC.
Recognized genetic syndromes account for only a small proportion of all cases of CRC. There are a number of genes that have been found to have an
importantrole in CRC carcinogenesis, these genes fall into one of three main categories (Oncogenes,tumor suppressor genes, and mismatch repair genes).