SFRP1 and tumor of parathyroid gland: However, deregulation of WNT/β-catenin signaling modulators has been detected in parathyroid tumors compared to normal glands: Promoter hypermethylation of inhibitors of the WNT signaling APC and RASSF1 [43,44], SFRP1 [45,46], and GSK3β [40] have been described in both benign and malignant parathyroid tumors, while hypermethylation of CTNNB1/β-catenin occurs in about one fourth of PAds [47].