Types of endometriosis

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There are 3 types of endometriosis lesions

From a didactic point of view, endometriosis lesions are classified into 3 major groups, which may be associated in the same woman.
In theory, endometriosis lesions can be found anywhere in the pelvis and abdomen, and more rarely in the thorax.

Superficial, peritoneal lesions

Superficial, peritoneal lesions are probably the most common, and are located in the peritoneum.

These are small, superficial lesions, whose depth of invasion does not exceed 5 mm.

They can take different forms:

Sometimes they are active, red lesions, very similar to the endometrium, often hemorrhagic, surrounded by an inflammatory reaction. (a)
Other lesions have a brownish color (b), or the appearance of black microcysts (c), testifying to an old hemorrhage.
Others are whitish, probably cicatricial, reflecting a healing process (d).

Cystic lesions of the ovaries

Cystic lesions of the ovaries (ovarian endometriomas) are hemorrhagic lesions that encyst under the ovarian parenchyma and progressively displace it.

Varying in size from a few mm to several cm, these lesions are not truly intra-ovarian cysts, like other types of ovarian cyst. They are the result of intra-ovarian invagination of a lesion initially on the surface of the ovary, which progressively invaginates into the ovary like a caterpillar into an apple.

This specificity makes their surgical treatment tricky, as the endometrioma and ovary are sometimes inseparable, which can result in damage to the ovary during removal of the cyst.

Deep, sub-peritoneal lesions

Deep, sub-peritoneal lesions (infiltration greater than 5mm) are hard, fibrous lesions in which hormone-dependent endometrial tissue is relatively poorly represented (15-20% of the volume of the endometriosis nodule).

These lesions tend to infiltrate the surrounding organs, behaving aggressively in a way reminiscent of tumors, leading to the emergence of severe forms that are increasingly difficult to remove.

Because of their fibrous composition, and ultimately lack of hormone dependency, the size of deep endometriosis nodules is little influenced by amenorrhea, which simply stabilizes the disease, but practically never causes it to disappear.

This explains why they can be found in post-menopausal women, where they can continue to be symptomatic despite definitive amenorrhea.

It is estimated that endometriosis may affect one in 10 women in France, although not all affected women are necessarily symptomatic or have severe forms such as those described above. It is likely that the disease follows a pyramidal distribution, with superficial lesions at the base (in the vast majority of women) and severe deep lesions at the top (in a minority of cases).