POLG and ductal breast carcinoma in situ: POLG1 is highly expressed (score +++) in all cases of DCIS (13/13) (Fig 1D-V and 1D-VI), 5/7 cases of low-intermediate grade IDC (Fig 1D-VII), all cases of high grade IDC (6/6) (Fig 1D-VIII), all cases of ILC (7/7) (Fig 1D-IX) and all metastatic breast carcinomas in regional lymph nodes (7/7) (Fig 1D-X and 1E and Table 1).