Last week I noticed a lump in the back of my leg, just below my knee. I don t know what caused it. It is not bruised. It s approximately the size of a golf ball, firm, and hurts when I press on it. Sometimes my calf and even foot feels tight. I do water aerobics 3 times a week, but I don t recall a sudden pain. I am 53 year old breast cancer survivor, so of course I m wondering how concerned I should be ...