POLB and ductal breast carcinoma in situ: Low nuclear POLβ protein expression in pure DCIS cohort was associated with aggressive clinicopathological parameters, including high nuclear grade (p = 0.001), comedo necrosis (p = 0.006), negative hormonal status (p < 0.001), positive HER2 status (p = 0.005) and with HER2 in molecular subtypes (p < 0.001) (Table 1).