Melanoma begins on the skin but can quickly travel into the body most often to the liver and brain.
The spot on President Carter's skin likely went unnoticed - until doctors discovered a lesion on his liver. Now, with four more lesions on his brain, Carter announced he`ll begin radiation.
But there`s another treatment he`ll likely receive - one that may help extend his life.
Stage 4 melanoma is a terminal diagnosis.
But in the last five years immunotherapy has helped patients put up a better fight against the deadly disease.
The therapy works by stimulating the body`s own cancer fighting cells.
Known as T-cells - they already recognize the cancer - they`re just not working well enough to contain the growth of tumors.
With Immunotherapy, doctors inject antibodies to help the t-cells better see and kill cancer cells.
The treatment is not effective in every case but immunotherapies are the first to impact a large number of patients