Endometriomas are cystic ovarian masses filled with old blood and tissue, stemming from endometriosis, a condition where tissue from the lining of the uterus, the endometrium grows outside the uterus. Endometriomas are often referred to as "chocolate cysts" due to the dark, reddish-brown fluid they contain. Endometriomas are a common finding in women with endometriosis and can indicate a more advanced stage of the disease. About 10% of young women will develop endometriosis, and about 17% to 44% of these women will also develop ovarian endometriomas and 28% of these women will have bilateral endometriomas.

Summary

Although endometriosis is a common disease affecting up to 15% of women of reproductive age, the mechanisms underlying the disease are not fully understood. Retrograde menstruation is a widely accepted cause of endometriosis. However, not all women who experience retrograde menstruation develop endometriosis, suggesting that other factors might contribute to its development. A recent study demonstrated a pathogenic role of Fusobacterium in the formation of ovarian endometriosis. In a cohort of women, 64% of patients with endometriosis but less than 10% of controls were found to have Fusobacterium infiltration in the endometrium (the lining of the uterus). This data supports an additional mechanism for the pathogenesis of endometriosis via Fusobacterium infection and suggests that eradication of this bacterium could be an approach to treat endometriosis