The present study shows for the first time that IL-6, a pro-inflammatory cytokine, overexpressed in sera or plasma of advanced high-grade serous ovarian cancer patients, is the single most informative cytokine out of 28 soluble factors able to enhance the diagnostic efficiency of conventional tools (RMI and ROMA) and biomarkers (CA125 and HE4) to discriminate between women with a malignant ovarian mass, benign ovarian pathology and healthy ovaries. This evidence concerns the gene IL6 and ovarian serous adenocarcinoma.