CLDN2 and thyroid cancer: For example, claudin-3 and claudin-4 were expressed at high levels in endometrioid adenocarcinoma [19] and prostate cancer [20]; claudin-10 expression was up-regulated in hepatocellular carcinoma [21] and thyroid papilloma [22]; claudin-2 has been reported to be up-regulated in thyroid cancer and endometrial cancer [23].