Skin Cancer FAQs
1. What causes skin cancer? Because skin cancer is caused by exposure to the sun’s ultraviolet rays many years before the skin cancer occurs, it has been difficult to convince the general population sun exposure was the cause. Most skin cancers develop in people who are older, at a time in which they are getting little sun exposure. For the most part, children spend more time out in the sun than adults, yet it is rare for a child to get skin cancer. This delay has caused confusion.
2. Why does it take so long after exposure for the skin cancer to develop? Ultraviolet light causes damage to the DNA of the living cell in the skin. If the damage is severe enough, the cell dies. We see this as peeling and blistering of the skin. If the damage is less severe, the DNA is permanently damaged but the cell does not die. This damaged cell, with its permanently changed DNA, gives raise to daughter cells which also have the altered DNA. Over many generations, and with additional DNA damage, the daughter cells may show the effects of the damage by changing their pigmentation (sun spots) or causing cancer. The change in color can occur in years. In children, we see this as freckles even in 5 year-olds (no one is born with freckles, they are always sun damage). It takes 20 or more years for skin cancer to develop.
3. Why does ultraviolet light cause skin cancer and the color near it in the spectrum, violet light, does not cause skin cancer? Light propagates in packets called photons. A photon of violet light has more energy than a photon of red light. When the violet photon hits an atom, it gives its energy to an outer electron. The energy transferred to the electron is insufficient to knock the electron completely from its atom. It jumps to a higher energy level and then releases its energy and returns to its original position in the atom. Ultraviolet light is the threshold in which the photon now has enough energy that the electron it hits receives enough energy to a its parent atom completely. An atom that has lost an electron has been ionized (ultraviolet light is ionizing radiation much like x-rays and gamma rays). Ionized atoms are unstable and will react chemically to nearby atoms. Random chemical reactions in the complex reactor that is the human body is dangerous occurance. The particular reaction that causes the DNA damage occurs when one of the two thiamine bases that happen to lie together in the DNA molecule ionizes. The reaction could then be a fusion of the two thiamine bases into a stable thiamine-thiamine dimer. Once this occurs, the daughter cells and all their subsequent generations get a poor copy of the DNA. A permanent mutation has occurred.
4. How do I know I have a skin cancer? I have been treating skin cancer for over three decades, and usually can tell when a skin change is cancerous, but not always. A typical skin cancer is a growth (a bump) that is new and growing. It often will eventually bleed as it gets larger. Careful towel drying after a shower may allow the cancer to heal enough to stop bleeding, but it bleeds again.