What Causes Thickened Endometrium?

Hello I am 36 years old with pcos. During an ultrasound my dr. found I had an endometrial lining that is 1.6cm. I am getting a d&c next week and I am scared it could be uterine cancer. I don't ovulate and was spotting for 3 weeks. Is uterine cancer common? What other causes could there be for that thick of a lining? Thank you for your time.