Sort of, but endometriotic growths aren’t quite the same as the endometrial lining in the uterus. They’re not actually true endometrial tissue; they usually have differences that are visible under the microscope. Theories about development include “retrograde menstruation,” in which menses flow back up through the fallopian tubes and into the pelvic cavity; however, most women experience retrograde menstruation, and don’t experience endometriosis, and some people who have never menstruated have been diagnosed with endometriosis.[1][2][3] Other theories involve transformation of other cells into endometriotic cells.[4]
So endometriosis is just uterine lining growing outside the uterus?
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•Last Updated: May 16, 2025
Endometriosis involves growths that are not identical to the uterine lining and have distinct differences that are observable under a microscope. Although hypotheses like retrograde menstruation suggest a cause, many women with retrograde menstruation do not develop endometriosis, and some individuals who have never menstruated can still be diagnosed with the condition.