Low cytoplasmic POLβ expression was significantly associated with larger DCIS size (p = 0.017), diffused type of DCIS (p = 0.025) high nuclear grade (p = 0.015), PR negativity (p = 0.046), HER2 positivity (p = 0.007) and higher proliferation index (Ki67) (p = 0.021) (Table 2 and Supplementary Table S3). This evidence concerns the gene MKI67 and ductal breast carcinoma in situ.