Although, the methylation analyses of Hoxa9 with large cohorts has shown that Hoxa9 is hypermethylated in both high-grade serous ovarian cancer (Montavon et al., 2012) and primary ovarian cancer patients, (Wu et al., 2007) the association of hypermethylation with the stage, histological types, grade, and ascites could not be established (Xing et al., 2015). This evidence concerns the gene HOXA9 and ovarian serous adenocarcinoma.