Aim: The retrospective evaluation of correlations between semi-quantitative breast-specific gamma imaging (BSGI) and invasive ductal breast cancer (IDC) sub-types. Materials and Methods: The biopsy specimen of 50 histologically-proven IDCs were retrospectively evaluated concerning receptor status, human epidermal growth factor receptor 2 (HER2/Neu) status, Ki-67 level and classification into IDC sub-types. These results were compared to the relative uptake factor (RUF) in BSGI. Depending on RUF, we described four categories to outline the predictive value of RUF. Results: A total of 50 IDCs with a mean diameter of 20.36 mm were included. RUF differed reliably between luminal-A and non-luminal-A IDCs. RUF exceeding 6.5 pointed to non luminal A-carcinoma, with a specificity and positive predictive value of 100%. RUF of less than 2.6 was unlikely to be associated with a non-luminal A-carcinoma (negative predictive value: 76.5%). Comparable results were calculated for the correlation between RUF and the K-67 level. Conclusion: RUF may help classify the sub-type of an IDC in addition to pathology.