Understanding What the Colors of Endometriosis Lesions May Tell Us

Endometriosis lesions can appear in many different colors during laparoscopy. They are often visualized as red, black, blue, brown, white, or even clear.

Because endometriosis has historically been described as a classic dark “powder-burn” lesion, many people are surprised to learn that lesions can actually look very different from one person to another.

Research suggests that the color of a lesion may reflect biological changes occurring in the tissue, such as bleeding, inflammation, immune activity, or scarring. At the same time, appearance alone cannot reliably determine how severe endometriosis is or how much pain someone may experience.

Still, understanding these patterns can be helpful. They offer clues about how lesions may develop and change over time. For physicians, recognizing that endometriosis can appear in different forms may improve detection during surgery and support ongoing research into how the disease behaves.

Black and Blue Lesions

Puckered black or dark blue lesions are the classically described “powder-burn” lesions noted in early surgical literature.

These lesions are thought to develop after repeated bleeding within an endometriotic implant. Over time, the blood breaks down and can become trapped within fibrotic tissue, giving the lesion its characteristic dark blue or black appearance.

These lesions are generally believed to represent older implants, containing degraded blood products within fibrotic tissue. Histological studies show they may contain:

• Endometrial glands

• Surrounding stromal tissue

• Intraluminal debris (degraded material trapped within gland structures)

Red and Pink Lesions

Red or pink lesions are often described as highly vascularized and inflamed.

During surgery they may appear as:

• Small red spots

• Vesicles

• Hemorrhagic areas

• Flame-like lesions

Studies examining immune cells within lesions have found higher numbers of macrophages in red-colored lesions. Macrophages are immune cells involved in early-stage inflammation and tissue repair, suggesting these lesions may be associated with more active inflammatory processes.

Because of these features, red lesions are sometimes thought to represent earlier or more biologically active stages of lesion development, although lesion color alone cannot reliably determine disease activity.

Clear Lesions

Some endometriosis lesions have very little pigmentation and may appear clear, translucent, or subtle during surgery.

These lesions can be more difficult to detect because they lack visible pigment. However, biopsy studies have confirmed that non-pigmented lesions can still contain endometriosis tissue.

Evidence also suggests that lesion appearance may change over time. Subtle lesions may evolve into darker lesions as the disease progresses.

Interestingly, atypical lesions—including clear, grainy, red, and flame-like lesions—appear to be more common in adolescents experiencing pelvic pain than the classic dark lesions described in older surgical literature.

Some studies have also found that clear and red lesions tend to occur in patients approximately a decade younger than those with black lesions, supporting the idea that lesion appearance may evolve with time.

White Lesions

White or scar-like lesions are often associated with fibrosis, the formation of scar tissue.

Histological studies (the microscopic examination of tissue and cells) suggest these lesions may represent areas where endometriotic implants have undergone scarring or regression, leaving behind fibrotic plaques.

Brown Lesions

Brown coloration is most commonly associated with ovarian endometriomas, often called “chocolate cysts.”

These cysts form when endometriotic tissue grows within the ovary and bleeds repeatedly with menstrual cycles. Over time, the trapped blood breaks down into iron-rich pigments, including hemoglobin degradation products, which give the cyst its characteristic brown appearance.

The fluid inside endometriomas often becomes thick and dark—sometimes described as tar-like—due to the accumulation of degraded blood products.

Mixed-Color Lesions

Many lesions display more than one color within the same implant.

This likely reflects multiple biological processes occurring simultaneously, such as:

• Bleeding

• Inflammation

• Scar formation

Surgical studies have shown that mixed-appearance and multi-colored lesions are common in endometriosis.

Endometriosis lesions can appear in many different colors during surgery, including red, clear, black, brown, and white.

These visual differences generally reflect biological processes occurring within the tissue, such as inflammation, bleeding, immune activity, or scarring.

Lesion appearance may also change over time. Early lesions may appear red, clear, or subtle, while older lesions may become darker or develop fibrotic white areas. Appearance can also vary depending on factors such as the menstrual cycle phase and hormonal influences.

References

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3. Nisolle M, Donnez J. Peritoneal endometriosis, ovarian endometriosis, and adenomyotic nodules of the rectovaginal septum are three different entities. Fertil Steril. 1997;68(4):585-596.

4. Martin DC, Hubert GD, Vander Zwaag R, El-Zeky FA. Laparoscopic appearances of peritoneal endometriosis. Fertil Steril. 1989;51(1):63-67.

5. Sophonsritsuk A, Attawattanakul N, Sroyraya M, et al. Macrophages and natural killer cells characteristics in variously colored endometriotic lesions: a cross-sectional analytic study. Int J Fertil Steril. 2022;16(2):108-114.

6. Agarwal N, Subramanian A. Endometriosis – morphology, clinical presentations and molecular pathology. J Lab Physicians. 2010;2(1):1-9.

7. Khashchenko EP, Uvarova EV, Fatkhudinov TK, et al. Endometriosis in adolescents: diagnostics, clinical and laparoscopic features. J Clin Med. 2023;12(4):1678.

8. Radiopaedia. Endometriosis. https://radiopaedia.org/articles/endometriosis

Research summarization support provided by Consensus.app (https://consensus.app).