I have 17 mm thick endometrial. is this cancer?

Maybe: If it is uniform, I am betting on a premalignant hyperplasia, but you want to have it sampled and sent to a pathologist. These can be tricky; see if you can get two of us to read it. I'm pleased that you did not say anything about invasion being detectable -- that's a good thing.

Depends: Depending on when in your menstrual cycle the pelvic ultrasound was done, a 17 mm endometrium may or may not imply a serious issue, but it does warrant further investigation such as repeat ultrasound ( if one was done right before the period) or possible endometrial biopsy, if original ultrasound was done right after the cycle. Talk to your gynecologist.

Thick uterine lining: So you have had as us and the lining is thick.In order to determine if this is just a normal growth or cancer a sample of the lining will need to be taken, like a d&c. The pathologist will than look under the microscope and see if the cells are abnormal. Cancer cannot be diagnosed by x-ray the first time...You have to have tissue.