MUC16 and neoplasm: However, although CA125 is overexpressed in 80% of epithelial ovarian cancer cases and is the tumor marker of choice for epithelial ovarian cancer (Bast, Hennessy & Mills, 2009), this marker naturally increases with ovulation and may be elevated with endometriosis, fibroids, and many other benign conditions (Etzioni et al., 2003).