Breast cancer FISH test is mainly for HER-2 (epidermal growth factor 2) to determine, because HER-2 sometimes suggests (++), if it is (++), it is not sure whether it is positive, or negative, then we have to use FISH test to determine whether HER-2 is positive, or negative. If it is positive, targeted therapy should be taken. If it is negative, targeted therapy is not needed. So, the purpose of FISH test is to determine whether HER-2 (epidermal growth factor 2) is positive or negative.