Endometriosis is a condition where tissue similar to the uterine lining grows outside the uterus. Despite its challenging symptoms, it is a benign condition, meaning it is not cancerous.
What Endometriosis Is
Endometriosis is a chronic inflammatory condition where endometrial-like tissue establishes itself outside the uterus. This misplaced tissue can be found on organs within the pelvis, such as the ovaries, fallopian tubes, and the outer surface of the uterus. The tissue behaves similarly to the uterine lining, thickening and bleeding with hormonal changes. Unlike menstrual blood that exits the body, this blood has no escape, leading to inflammation, pain, and scar tissue formation.
This condition can cause significant pelvic pain, especially during menstrual periods, and may also lead to painful bowel movements or urination. In some cases, it can contribute to fertility challenges. While the exact cause of endometriosis is not fully understood, theories include retrograde menstruation (menstrual blood flowing backward into the pelvic cavity) and changes in embryonic cells or immune system function.
Why Endometriosis Is Not Cancer
The fundamental distinction between endometriosis and cancer lies in their biological nature: endometriosis is a benign condition, whereas cancer is malignant. Benign growths, like those in endometriosis, do not typically invade surrounding tissues aggressively or spread to distant parts of the body in the way malignant cells do. Cancer cells exhibit uncontrolled, abnormal proliferation and can metastasize, forming secondary tumors throughout the body.
Endometriotic tissue, even when found outside the uterus, consists of cells that are morphologically normal, differing from the atypical and often mutated cells characteristic of cancer. Although endometriosis can be invasive locally and form adhesions, it does not possess the destructive invasiveness or the capacity for widespread metastasis seen in cancerous growths. The prognosis for endometriosis typically involves managing chronic pain and potential infertility, but it is rarely life-threatening, which contrasts sharply with the life-threatening nature of untreated cancer.
The Rare Link to Certain Cancers
While endometriosis itself is not cancer, a very rare association exists with certain types of ovarian cancer, predominantly clear cell and endometrioid carcinomas. This increased risk is slight, with studies indicating that the probability of malignant transformation in endometriotic lesions is approximately 0.5% to 1%. This is a transformation of existing endometriotic lesions into cancer, not that endometriosis is inherently cancerous or always progresses to cancer.
Researchers have identified specific genetic mutations (e.g., ARID1A, KRAS, PIK3CA) in both endometriotic lesions and associated ovarian cancers, suggesting shared molecular pathways for this rare transition. The overall lifetime risk of developing ovarian cancer remains low, even for individuals with endometriosis. However, more severe forms of endometriosis, such as deep infiltrating endometriosis or ovarian endometriomas, may be associated with a slightly higher relative risk compared to milder forms.