The fact that endometrioma can be viewed as a precursor of endometrioid ovarian cancer [19] underlines the value of exploring whether RANK expression might be related to the malignant profile in this histotype of epithelial ovarian cancers (EOC), considering the other two main EOC histotypes, serous and mucinous. The gene discussed is TNFRSF11A; the disease is ovarian carcinoma.