Integration of genes associated with exposure to PCBs, and breast cancer and endometriosis based enriched disease analysis showed that there were 16 endometriosis genes overlapped with breast neoplasms—AREG, C10ORF10, CLDN1, CYP19A1, DKK1, EGFR, ESR2, FOS, IGF1, KRAS, NCOA1, NCOR1, NR2F6, PGR, RARB, and STC2 (Table 2 and Table 6). The gene discussed is ESR2; the disease is breast cancer.