Endometriosis (EM) is one of the most common benign diseases in gynecology, with a prevalence of 5%-15% in women of childbearing age.Although EM is a benign disease, it has biological behaviors similar to malignant tumors, such as local infiltration, distant metastasis, and easy recurrence, making it a difficult disease to treat in gynecology. Histological and epidemiological data also clearly show that EM can be malignant, with the ovary being the most common site of malignancy and the main pathological types being ovarian endometrioid carcinoma and clear cell carcinoma. The literature reports that EM patients have a 0.7-2.5% chance of developing malignancy over an average of 8 years of disease. With the increasing incidence of EM in recent years, the incidence of ovarian cancer arising from endometriosis (OCEM) has also increased significantly. It is of great theoretical and practical importance to study the mechanism of EM malignant transformation, to screen the high-risk groups for EM malignant transformation, and to develop appropriate individualized medical interventions for EM patients. Studies have suggested that EM malignancy may be associated with genetic variants, high local estrogen levels, immunotoxicity, and environmental factors. In recent years, the relationship between loss of heterozygosity (LOH) and EM malignancy has received increasing attention. Our research group first reported the distribution of LOH in 12 OCEM patients in 2011. We hypothesize that LOH is closely associated with EM malignancy; meanwhile, there may be some other unknown novel genes that are involved in the process of EM malignancy.