I have a pure white cat. He is 4 years old. He loves the out doors and from the first time he went out, on a sunny day, he has had sun block applied to his ears to protect them. This morning however, I discovered a small black crust on the side of his ear. I rubbed it off, applied his sun block liberally and he went outside. I will keep a close eye on his ear to see if it returns.What are the odds on this being the first signs of Cancer..am I over worrying?