Stage I vulvar cancer is divided into stages IA and IB. In both IA and IB, cancer is found only in the vulva or in the vulva and perineum (area between the rectum and the vagina) and the tumor is 2 centimeters or smaller. In stage IA, the tumor has spread 1 millimeter or less into the tissue of the vulva. In stage IB, the tumor has spread more than 1 millimeter into the tissue of the vulva.