I came back from college last weekend and my sheltie had a huge black/blue area on her abdomen - probably about 10 inches by 5 inches with definate lines (not like a bruise). She isn't itchy or sore to the touch, it isn't scaly or rough. There is no hairloss, but she has had dandruff problems recently and just shed out big time. This spot wasn't there last weekend. What could it be?