It involves the division of body cells and abnormal cell growth and can occur almost anywhere in the body.
In "Stanley's Cup", Stan Marsh becomes a coach to the Park County Pee-Wee Hockey Team. One of the teammates has leukemia and dies in a hospital, after the team loses a hockey match to the Detroit Red Wings.
In "Breast Cancer Show Ever", Wendy Testaburger tries to raise awareness for breast cancer, but is heavily ridiculed by a naive Eric Cartman. In an effort to motivate Wendy to overcome her issues with Cartman, Principal Victoria mentions that she herself is a breast cancer survivor and had to take significant actions to overcome it.
In "Tonsil Trouble", although the episode focuses heavily on HIV and AIDS, cancer is mentioned often as part of a recurring joke. Cancer is noted throughout the episode to be the disease of the time, akin to a fad, with AIDS being written off as merely an "'80s and '90s disease".
In "Medicinal Fried Chicken", Randy Marsh induces testicular cancer by the use of a microwave oven. This causes his testicles to grow to a comically enormous size. When this plan works, he convinces his friends to do the same.