Freebase(0.00 / 0 votes)Rate this definition: Arbol is a programming language which has been primarily developed for use in Genetic Programming experiments. It is a functional programming language inspired by the ideas of other small and esoteric languages.
Causes. In most cases of colon or rectal cancers, the cause or causes are unknown. Defects in genes that normally protect against cancer play the major role in causing polyp cells to continuously change and become cancerous.
Possible triggers for this immune system reaction include: 1  Infections, such as hepatitis B and hepatitis C. 2  Blood cancers. 3  Immune system diseases, such as rheumatoid arthritis, lupus and scleroderma.  Reactions to certain drugs.