Uterine cancer!

In a previous post you answered that a buildup of the lining can lead to uterine cancer...why is this?  What are the reasons for this to happen?  Why can't one have a period after menopause?  My OB/GYN stated that the cervix closes when there is no shedding of the lining and there should be no more bleeding unless there is pressure up inside causing bleeding to occur. Of course this causes concerns stated in another post that was answered.  I just find it hard to understand that you can have bleeding from excess estrogen during nemopause but you can't have bleeding due to the cervix being closed.  Please explain.

[Machelle Seibel, MD]

A. Estrogen causes the lining of the uterus to increase in thickness. This happens in nature to prepare the lining of the uterus to receive an egg and allow it to implant and grow. But during the reproductive years, progesterone is also produced and that stops the lining form building up to high. If one doesn