What condition is characterized by the presence of endometrial tissue outside of the uterus?

Endometriosis is characterized by the presence of endometrial tissue, which normally lines the inside of the uterus, growing outside of the uterus. This condition can lead to a host of symptoms, including pelvic pain, especially during menstruation, heavy periods, and sometimes infertility. The ectopic endometrial tissue can be found in various locations within the pelvis, including the ovaries, fallopian tubes, and the pelvic lining, among other areas. The misplaced tissue continues to behave hormonally, responding to menstrual cycles, which can cause pain and inflammation.

This distinctiveness of endometriosis, marked by the growth of endometrial-like tissue outside the uterine cavity, is what sets it apart from other conditions mentioned. Ovarian cysts are fluid-filled sacs on the ovary, while pelvic inflammatory disease refers to an infection of the reproductive organs. Uterine fibroids are noncancerous growths within the uterine wall itself. None of these conditions specifically involve endometrial tissue growing outside of the uterus, which is the hallmark of endometriosis.