Could be a form of cell cancer....and also, when people get older, they do have these black patches of skin growing on their bodies....they are usually harmless, and can be "scratched off"......
I had one on my back, saw the doctor and she told me it wasn't any problem, that older people get them, they are not cancerous...
But the one on this lady's head, has grown...she should have gotten it "removed" before letting it get this big!