They can do a biopsy after removing the tumor. in fact I think it is the normal protocal in hospitals to do biopsys on any tumors to find out if it is malignant or benigh. So your mother will know before she is even released from the hospital after the surgery. Also when the doctor was examining your mother and located the tumor he would have done test to see if the fluid that was leaking from it contained cancer cells which it would have if it was malignant for a cancer tumor produces cancer celled filled fluid. since she has not been told that cancer cells were found in the fluid she does not have cancer. so you can relax.. Sorry about your kitten.Take care.