Special AT-rich sequence-binding protein 1 (SATB1) is a nuclear matrix protein which interacts with specific regions of DNA, ensuring its proper organization and function in the cell. The expression of SATB1 was primarily found in thymocytes, but its increased levels were observed in various types of cancers. However, the knowledge of the function and application possibilities of this protein is still limited. The aim of this study was to investigate the expression of SATB1 protein using immunohistochemistry and tissue microarray (TMA) technique and determine its possible relationship with the proliferative marker Ki-67, estrogen a (ER) and progesterone (PR) receptors as well as grade of histological malignancy (G). The study was performed on material of 48 archival invasive ductal breast cancers (IDC). The TMAs were prepared with the use of 0.6 mm diameter punches. Immunohistochemical reactions were carried out using antibodies against Ki-67, ER, PR and SATB1 proteins. The intensity of the nuclear reaction was evaluated using a light microscope and computer-assisted image analysis. Expression of Ki-67 and SATB1 protein was observed in 89.58% and 31.25% of cancer cases, respectively. 62.5% of tumors were classified as ER-positive, and 47.92% as PR-positive. Statistical analysis showed a moderate positive correlation between Ki-67 and SATB1 expression (r = 0.291, p = 0.045 independently on the receptor status, and r = 0.392, p = 0.032 in ER-negative tumors). The expression of the Ki-67 antigen increased with higher grade of histological malignancy (G). The results suggest that SATB1 protein may play an indirect role in the cell proliferation and should be evaluated in relation to the other markers. Further studies concerning determination of its role in cancer progression and metastasis, in terms of application as therapeutic target and prognostic marker, are recommended.