STAR and invasive ductal breast carcinoma: Next, the expression of Star-PAP in human breast cancer tissues was examined by analyzing the public data sets.14, 15, 16 Although highly expressed in normal mammary tissues, Star-PAP was downregulated in ductal carcinoma in situ (Figure 1e), invasive ductal carcinoma (Figure 1f) and even the stroma of invasive ductal carcinoma (Figure 1g).