Could s simple 2 cm ovarian cyst on ultrasound that shows up as small enhancing cyst on ct scan be malignant in a premenopausal woman? No change in yr

Low chance. If the cyst is described as simple then there is only fluid inside. So no other growths inside the cyst. Simple cysts are almost always benign. The fact that it hasn't changed in a year is also a good sign. Overall, very low chance of being malignant. Ask your doctor to monitor it every year.