If i'm an 18 year old male who smokes around 10 cigarettes a day, will i necessarily get cancer?

Increased risk.: Smoking significantly increases the risk for many major cancers. This risk soars with the quantity & years smoked. As a surgeon who removes bladders and kidneys due to smoking-related cancers, i strongly discourage anyone from smoking. But cancer arises from an incredibly complex interplay between genes & the environment, so it is usually not possible to predict who will necessarily get cancer.

No, but...: I promise that your smoking will impair your athletic performance, your best sexual performance, and damage your lungs enough so your middle age and later will be a lot less fun. Break the addiction now by any means you can -- i suggest doing it as your best revenge against the jackass tobacco company ceo's that deceived you in the first place. Be tough and strong and good luck.