WHAT CAUSES CANCER?

Everything. We all carry cancer within us. What you should be asking is 'what turns it on'.

from the unit "it is generally agreed that 90% of all u/s cancers are due to an excess of nitrates herbicides and pesticides, in the food chain and water supply" the implied requirement being the understanding that, as the u/k is a lot smaller and far more intensively farmed than the u/s, the problem is of graver significance.

from an address by sir richard doll regus professor of medicine at oxford university, on cancers and their causes, (which a lot of females detest because of his appraisal on the cause of cervical cancer and it being a viral infection) while pure alcohol is not carcinogenic in animals it readily combines with tobacco smoke, to form carcinogenic compounds that go straight for the oesophagus, this is substantiated, by the highest rate of esophageal cancer in europe being in Brittany and Normandy, and is characterised by their liking for cider and cider based liqueurs.

(food and drink made from decomposing fruit and vegetables are highly carcinogenic)

as the above is now 26 years old, and sir richard doll prediction of a vaccine for cervical cancer which is morality in a syringe, has become embedded in our culture, society has still failed to respond to the findings of technology, see the "chinese cancer detectives" by edward goldwyn presented for BBC2 Horizon in 1980, as even chinese pheasants can respond to a change in diet and habits if it offsets cancer of the oesophagus!!!
the highest incidence rate of esophageal cancer is in N E Iran where the risk factor is 20%.
there is also a long list of occupational cancers, which are attributable to things like vinyl chloride (pvc) and say isopropyl oil (isopropylene manufacture)

to explain in simplistic terms nitrates stimulate cell growth in plants, to accelerate their growth, and shorten their growing period, when they enter the human body by ingestment either by eating food enriched with nitrates or in water where they enter the water supply by running of the land enriched by them, they stimulate abnormal cell growth in it, which results in a cancerous growth.

Source:
From T101 a foundation course in technology presented by the open university

"The Cancer Detectives of Lin Xian" are a team of Peking scientists seeking to stem the unusually high incidence of esophageal cancer in one Chinese country. About one out of four residents of Lin Xian dies from the disease, and one reason, according to this report, may be the carcinogens found in their diet.
Richard Prevost is the narrator.

They don't know. There are things that increase risks. There are gene mutations that put you at as high as a 90% risk, that's pretty freaking high, but they still don't say it was caused by__...or it doesn't on any of my reports or notes.

No one knows what exactly causes cancer. It could caused by genetics, stress, unhealthy eating habits, not exercising, smoking and a lot of other things. If you notice anything unusual like any cancer symptoms then seek medical help if you having problems.

Cancer is a mutation in the replication of cells (to my knowledge). Nothing "causes" cancer except the mutation, however, certain things can put you at risk. Smoking puts you at higher risk for Lung Cancer. Being an African American male puts you at higher risk for prostate cancer and long, unprotected sun exposure puts you at higher risk for skin related cancers. Please note that I am not a licensed medical professional. If you believe you may have signs of cancer or any other diseases, contact your doctor or seek emergency care if believed to be necessary. This answer is not intended for curing or treating cancer or any disease.