Archived serum and tumor tissue samples are analyzed for synuclein-γ (SNCG) expression and other biomarker expression, including TP53 (p53), HER-2, folate receptor alpha (FOLR1), estrogen receptor (ER), progesterone receptor (PR), phosphatase and tensin homolog (PTEN), phosphorylated AKT (pAKT), pERK, and p16 by microarray analysis, IHC assays, and western blot. Results are then compared with patients' existing clinical, demographic, and pathology data, including history of breast cancer (metachronous) or breast cancer diagnosed at the same time as the endometrial cancer (synchronous).