Canceris a group of diseases involving abnormalcell growthwith the potential to invade or spread to other parts of the body.Not all tumors are cancerous;benign tumorsdo not spread to other parts of the body.Possiblesigns and symptomsinclude a lump, abnormal bleeding, prolonged cough, unexplainedweight lossand a change inbowel movements. While these symptoms may indicate cancer, they may have other causes.Over 100 cancers affect humans.
Tobaccouse is the cause of about 22% of cancer deaths. Another 10% is due toobesity, poordiet,lack of physical activityand drinking alcohol.Other factors include certaininfections, exposure toionizing radiationand environmental pollutants.In thedeveloping worldnearly 20% of cancers are due to infections such ashepatitis B,hepatitis Candhuman papillomavirus(HPV).These factors act, at least partly, by changing thegenesof a cell.Typically many genetic changes are required before cancer develops.Approximately 5–10% of cancers are due to inherited genetic defects from a person's parents.Cancer can be detected by certain signs and symptoms orscreening tests.It is then typically further investigated bymedical imagingand confirmed bybiopsy.
Many cancers can be prevented by not smoking, maintaining a healthy weight, not drinking too muchalcohol, eating plenty of vegetables, fruits and whole grains,vaccinationagainst certain infectious diseases, not eating too much processed and red meat, and avoiding too much sunlight exposure.
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