Anti-nuclear antibodies (ANAs) are autoantibodies synthesized in response to the cell nucleus contents and use as biomarkers of systemic autoimmune diseases. Inflammation, apoptosis and necrosis of the cells are consequences that accompany breast cancer against which autoantibodies will be produced. In this study, we aimed to evaluate the presence of ANAs and anti-extractable nuclear antigens (anti-ENAs) in breast cancer. A total of 33 luminal A and luminal B breast cancer patients were assessed for presence of ANAs and anti-ENAs. All the patients had received hormone therapy at least for 6 months before the tests. Patients were screened to ANAs by indirect immunofluorescence on human epithelial type 2 (HEp-2) cells. AESKUBLOTS® ANA-17 comp kit was used to identify the concentrations of U1-snRNP, snRNP/Sm, SmD1, dsDNA, SS-A/Ro 60, SS-A/Ro 52, SS-B/La antibodies. Fifteen (45.5%) patients were luminal A and 18 (54.5%) patients were luminal B. The median of age was 57 and the median of tumor size was 25. 19 (57.6%) patients had grade I or II and 14 (42.4%) had grade III. 3 patients had ANAs test positive. All the patients who had positive ANA test were luminal A breast cancer and had grade I or II tumors and positive lymph node, whereas, pathological tumor stage were varied. No statistically significant association was found between ANAs positivity and molecular subtype, age, body mass index (BMI), grade, tumor stage or lymph node involvement. Moreover, there were negative correlations between the anti-U1-snRNP and anti-dsDNA with Ki-67 and a correlation between anti-snRNP/Sm and anti-SS-A/Ro 52 was found. Comparing with luminal A, anti-U1-snRNP and antisnRNP/Sm concentrations were statistically significantly lower in luminal B tumors (p= 0.015 and 0.016 respectively). Patients who had high grade tumors showed low concentrations of anti-snRNP/Sm (p=0.027), whereas patients who had lymph node metastasis showed high concentrations of anti-U1-snRNP (p=0.031). ANAs positivity was more common in luminal A breast cancer patients compared with luminal B. Anti-U1-snRNP and anti-snRNP/Sm concentrations were lower in luminal B. Moreover, patients who had high grade tumors showed low concentrations of anti-snRNP/Sm, whereas those who had lymph node metastasis showed high concentrations of anti-U1-snRNP. [ABSTRACT FROM AUTHOR]