If I'm not mistaken, visible malignancies take quite a while to form and wouldn't be apparent during the healing process of a burn. Not to say that a mark that appeared as a result of a burn couldn't one day become malignant, but I think that it would happen much much later. And even if it did become something to worry about, there's a large window of time in which to have it treated with probably the highest rate of being 100% cured out of any other form of cancer. In short - don't worry too much about it.
