I recently started reading about thoracic endometriosis and discovered a number of very clear, interesting images. See, e.g., https://www.drseckin.com/thoracic-endometriosis-syndrome-endometriosis-of-the-diaphragm or https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6684338/.

I was surprised that endometriosis in these images appears white. Because the tissue is similar to the tissue lining the uterus, I (a non-medical expert who doesn't spend much time looking inside organs) presumed it would be red or pink-ish.

So, why does endometriosis look white? And, as a follow-up question, does the tissue lining the inside of the uterus also look white?


The lining (endometrium) of the uterus is red-pink, as you can see from endoscopic photos of the uterus here.

The tissue of endometriosis lesions is not the same but similar to the lining of the uterus and can be red or white, according to the study: Using Location, Color, Size, and Depth to Characterize and Identify Endometriosis Lesions in a Cohort of 133 Women (Fertility and Sterility, 2008):

357 of 544 lesions felt to be endometriosis by the surgeon had positive histology. Mixed color lesions most commonly contained endometriosis (76%), with the percent of positive lesions being similar between single color groups. 58% (164/283) of subtle (red or white) lesions were positive for endometriosis. Thirty women had only red or white lesions, and 18 (60%) had at least one lesion positive for endometriosis.

Endometriosis lesions can trigger the development of adhesions and internal scars, which are made of fibrous tissue, which is white. According to Mayo Clinic:

Surrounding tissue can become irritated, eventually developing scar tissue and adhesions — abnormal bands of fibrous tissue that can cause pelvic tissues and organs to stick to each other.

The page on drseckin website you linked contains images of endometriosis with white tissue, which is, according to the text over the images, due to scarring or adhesions, so not from the endometriosis lesions themselves.

  • I noted in my question that endometriosis is similar to uterine lining, so I think the copied text from Mayo Clinic is a bit overkill...
    – user17719
    Mar 3 '20 at 14:53
  • @artificial_moonlet, I'm not sure if I understand your comment. A doctor cannot discern between endometrial tissue and adhesions just by laparoscopy (endoscopy of the abdominal cavity), but by a histological examination of a sample. It can be endometrial tisue or adhesions that can be white.
    – Jan
    Mar 3 '20 at 14:57
  • The copied text from Mayo Clinic is superfluous, because I didn't ask for a definition of endometriosis. I'm trying to understand why images labeled with endometriosis show white tissue; unless, of course, the white stuff isn't endo tissue but actually scar tissue?
    – user17719
    Mar 3 '20 at 15:07
  • @artificial_moonlet, the photos of endometriosis you linked have the text over them, which says, that the white tissue you see is either from scarring or adhesions. I also edited my answer to make it more clear.
    – Jan
    Mar 4 '20 at 10:48

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