In 2009, the Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk concluded that smoking is associated with breast cancer and that there is a consistent causality between second-hand smoke exposure and premenopausal breast cancer (1).
The International Agency for Research on Cancer (IARC), evaluated the results of numerous studies and concluded that evidence for tobacco smoke carcinogenicity in breast cancer exists (2). 

The European Prospective Investigation into Cancer and Nutrition study found higher risk of breast cancer for former/current smokers or those exposed to second-hand smoke (3). Other risk factors are: the duration of smoking, number of cigarettes smoked, age at initiation, and years of cessation (4,5). 

References

1. Johnson KC, Miller AB, Collishaw NE, et al. Active smoking and secondhand smoke increase breast cancer risk: the report of the Canadian expert panel on tobacco smoke and breast cancer risk (2009). Tob Control. 2011;20(1):e2.

2. Secretan B, Straif K, Baan R, et al; WHO International Agency for Research on Cancer Monograph Working Group. A review of human carcinogens-Part E: tobacco, areca nut, alcohol, coal smoke, and salted fish. Lancet Oncol. 2009;10(11):1033–1034.

3. Dossus L, Boutron-Ruault MC, Kaaks R, et al. Active and passive cigarette smoking and breast cancer risk: results from the EPIC cohort. Int J Cancer. 2014;134:1871–1888.

4. Xue F, Willett WC, Rosner BA, Hankinson SE, Michels KB. Cigarette smoking and the incidence of breast cancer. Arch Intern Med. 2011;171(2):125–133.

5. Gaudet MM, Carter BD, Brinton LA, et al. Pooled analysis of active cigarette smoking and invasive breast cancer risk in 14 cohort studies. Int J Epidemiol. Epub 2016 Dec 28.