The word cancer implies that soemthing is not benign actually..I am a member of the ehalthcare comunity, and you may be slightly confused..
Most women are greatly helped by birth control when they have endo., because of the intense pain and pretty heavy bleeding.. Birth control controls this...
It is very common for women with endo to be treated with birthcontrol, and the mirena iud is a good treatment as well.
Endometriosis is not cancer at all, it is where the uterine type tissues are actually found outside of the uterus... They also react to the montly cycle of women, so if you are not on birth control you will have painful bleeding from these tissues
http://www.Endometriosisassn.Org/endo.Html
this is an endometriosis association