The expression rate of POU5F1/Oct-4 was lower in DCIS than in mucinous carcinoma, IDC and Paget’s disease; but the difference was not statistically significant (40.00 % vs. 44.44 % vs. 57.65 % vs. 100.00 %; P = 0.216). Here, POU5F1 is linked to ductal breast carcinoma in situ.