"How did this skin cancer form?" is a common question asked. "Did the bad sunburn 20 years ago cause the skin cancer or was it going to the beach last summer or neither of these?" Today I want to talk a little bit about how cancer develops so you can understand what is going on "inside" the tumors.
Skin cancer, like other cancers, does not develop overnight but likely begins to grow after the DNA of the cells gets damaged. This is called the multiple hit hypothesis and refers to multiple points of damage to the genetic material of the cells ("DNA") that leads to cancer development. It is not known how many points of damage are needed to cause the different forms of cancer.
Some people may be predisposed to skin cancer because the DNA of their skin cells may damage easily or because they were born with a "damaged" mole (meaning that even at birth the mole has some inherent damage). People with very fair skin may sunburn very easily and each of these sunburns does more damage to the DNA of the skin cells and thus can lead to cancer. Also, individuals with many moles at higher risk because each mole becomes a target for sun damage and can be adversely affected by the sun. The cells of the skin are continually replicating themselves so any damaged cell will make copies of itself and it does not take long to go from one damaged, cancerous cell to hundreds of thousands! It is this abnormally fast and poorly controlled replication of abnormal cells that defines cancer. This process does not happen quickly so the sunburn 20 years ago may have been the beginning of the damage and sunburn last week may have completed the multiple hits necessary for cancer.
So how does the body attempt to stop the formation of cancer? The goal is to prevent the replication of abnormal cells and the body has many natural mechanisms of doing so. The cells of the skin (and other organs) are able to correct many forms of damage to their DNA, thus providing protection against cancer causing agents. The cells are also programmed to die at certain times and no longer make copies of themselves. This is important as a damaged cell may recognize it is damaged and then not continue to proliferate. If the cells do not correct the damage and do not cease to proliferate, at times the immune system can attack these cells.
Unfortunately, the cancerous cells often overcome the body's natural defense systems and cancer begins to grow. For this reason, it is important to prevent the damage from ever occurring. Sun protection is the best way to do this, so remember to apply sunscreen every two hours when outside and wear protective clothing. Your body has a lot of natural protection but it also needs your help!