PTP4A1 and neoplasm: Interestingly, there was a lower expression of PTP4A1 in AciCC and DC (Additional file 1 Supplementary Fig. S3B), and all these tumors that expressed PTP4A1 were the non-myoepithelial types of SGTs, which suggested that PTP4A1 might function in tumor epitheliums, but not myoepithelial cells.