Endometriosis is a common health problem in women. It gets its name from the word endometrium, the tissue that lines the uterus (womb). In women with this problem, tissue that looks and acts like the lining of the uterus grows outside of the uterus in other areas. These areas can be called growths, tumors, implants, lesions, or nodules.

Most endometriosis is found:

• on or under the ovaries
• behind the uterus
• on the tissues that hold the uterus in place
• on the bowels or bladder

 Endometriosis rarely grows in the lungs or other parts of the body. This "misplaced" tissue can cause pain, infertility (not being able to get pregnant), and very painful periods.