New knowledge and insights about the malignant transformation of endometriosis.

Endometriosis may be a definitive risk factor for ovarian cancer, the most fatal gynecological cancer. The ability of endometriosis to transform into malignancy, first described by Dr. Sampson in 1925, is considered a rare occurrence, affecting approximately 1% of ovarian endometriomas. Recently we conducted a retrospective study regarding the malignant transformation of endometriosis in Japanese women. Many studies have reported a consistent correlation between endometriosis and ovarian cancer according to histological subtypes. However, the existing epidemiological evidence linking this association is insufficient to define the role of endometriosis as a cause of ovarian cancer and to influence changes to current clinical practice. Prospective cohort studies are therefore needed to clarify this issue. Additionally, the results of many molecular studies are conflicting, and earlier studies showing the molecular aberrations involved in genomic instability and mutation that enable malignant transformation have not been replicated in later studies. Careful long-term observation of a patient with endometrioma is required to detect possible subsequent incidence of malignant transformation. More importantly, a precise strategy should be set up for better prevention, early detection, specific diagnosis and treatment targeting molecular pathogenesis to understand the mechanisms of endometriosis-associated ovarian cancer. Clinicians need to be aware of the increased ovarian cancer risk in women with endometriosis.