Not being a doctor a do not know? What does he suggest next? Sometimes they can't tell until they do surgery. The odds of Ovarian cancer are less than 2% I am not sure for other cancers. I have had three cancer scares in my life that all turned out negative. My philosophy is not to worry until the doctor tells me to worry. When I did get ovarian cancer everything happened fast I was at the oncologist the next day and in surgery in 5 days. My GP's nurse was nice to me and she had never been nice to me so I knew something was up. It is hard not to worry.
This could be an ovarian cyst or a uterine fibroid. Most gynecologic masses / tumors (uterine and ovarian) are benign and do not require removal of any organs. And not all masses need to be removed either. Fibroids tend to shrink after menopause when estrogen production lessens so there is no need to remove them if the symptoms are manageable.
Many ovarian cysts resolve on their own too but typically need to be removed if they look suspicious or get to be bigger than about 7 cm (due to the concern of ovarian torsion). Do you have a copy of the ultrasound report? It usually lists the characteristics of the mass and if there is any free fluid (ascites) in the pelvis. There are certain characteristics that are more concerning than others.
Ovarian cancer is scary but rare. Uterine cancer is also rare. Unfortunately, female organ removal is grossly overused and there are lasting effects on long-term health as well as quality of life. It is therefore important that we understand our diagnosis and all treatment options along with the short and long-term consequences of those treatments. If this mass looks suspicious, you will want a gynecologic oncologist to do the surgery.
I had a 9.5 cm ovarian cyst. Even though my surgeon waited for the results of the frozen section while I was under anesthesia and the results were benign, he proceeded to remove all my sex organs. My life and health have been upended as a result.