Study Finds Link Between Larger Endometriomas and Ovarian Cancer

A study links the size of cysts associated with endometriosis with coexistent ovarian cancer.

A relationship between endometriosis and ovarian cancer has been acknowledged for more than a decade,1 but a new study that evaluates data collected from 800 patients over 10 years finds a connection between the likelihood of ovarian cancer and the duration of endometriosis and the size of the cysts associated with the disease.2

Endometriosis occurs when tissue that normally lines the uterine lining grows outside it, involving the ovaries, fallopian tubes and the pelvis. The disorder can cause extreme pain to women in their child-bearing years and interfere with conception. Treatments include surgery and taking hormone therapy.

A 2008 literature review by Nezhat et al found a prevalence of endometriosis in patients with epithelial ovarian cancer, “especially in endometrioid and clear cell types” at levels higher than the general population. Certain genetic alterations were found to be especially common, and endometriosis was linked to a “chronic inflammatory state leading to cytokine release.” The cytokines promote cell division, differentiation, and other processes that are similar to cancer growth. The review said much more work was needed to detail the link between endometriosis and ovarian cancer.1

A 2016 review reported that 80% of endometrosis-associated malignancies are found on the ovary, and that the condition is associated with “a remarkably high increase of ovarian cancer risk.” When these cancers occur, the patients tend to be younger, Krawczyk et al, reported.3

Now, a study in the International Journal of Gynaecology and Obstetrics2 tracked women from a tertiary care hospital whose surgery confirmed their diagnosis of endometriosis during the period from January 1, 2010, and December 31, 2019. The study was done to determine how often patients with endometriosis also had cancer; patient details were obtained from electronic records, and investigators conducted analysis to determine which independent risk factors were associated with cancers.2

Of the 800 patients, 104 (13%) had a coexistent malignancy, including 50 cases of ovarian cancer (6.2%); 33 cases of endometrial cancer (4.1%); 7 cases of patients who had both ovarian and endometrial cancer (0.9%); and 14 cases of breast cancer (1.8%).

Cancer was associated with increasing age, for an odds ratio (OR) of 1.13 (95% CI, 1.09-1.16); higher levels of cancer antigen 125 (OR, 1.002; 95% CI, 1.001-1.005); postmenopausal status (OR 6.2; 95% CI, 2.0-19.2); and having endometriosis more than 5 years (OR, 4.7; 95% CI 2.5-9.0). Having endometriomas larger than 8 cm was predictive than of coexistent malignancy.


1. Nezhat F, Datta S, Hanson V, Pejovic T, Nezhat C, Nezhat C. The relationship of endometriosis and ovarian malignancy: a review. Fertility and Sterility. 2008;90(5):1550-1570.

2. Dahiya A, Sebastian A, Thomas A, George R, Thomas V, Peedicayil A. Endometriosis and malignancy: the intiriguing relationship. Int J Gynaecol Obstet. Published online January 8, 2021. doi: 10.1002/ijgo.13585.

3. Krawczyk N, Banys-Paluchowski M, Schmidt D, Ulrich U, Fehm T. Endometriosis-associated malignancy. Geburtshilfe Frauenheilkd. 2016;76(2):176-181. doi: 10.1055/s-0035-1558239