PCNA and neoplasm: A panel of common markers have been used for the diagnostic of EC in clinical practice, including enzymes [TOPOII, glutathione S‐transferase (GST)‐π], oncogenes (c‐Myc, CyclinD1, EGFR, Her2/Neu), tumor‐specific antigens (MDR), tumor suppressor genes (p53, p21, p27), and tumor proliferation markers (Ki67, PCNA, BCL‐2, Bax).