Although alcohol is a well-established risk factor for breast cancer, it may be more strongly linked with lobular breast cancer than with ductal breast cancer. These results were published in the Journal of the National Cancer Institute.
Research suggests that each 10 gram (slightly less than one drink) increase in daily alcohol consumption increases the risk of breast cancer by roughly 7%-10%.  This is a fairly modest increase in risk, but breast cancer is a common cancer; even a small increase in risk may translate into many additional cases on a population level.
Several studies have suggested that the relationship between alcohol and breast cancer varies by the hormone receptor status of the breast cancer. Alcohol tends to be more strongly linked with hormone receptor-positive breast cancer than with hormone receptor-negative breast cancer.
Fewer studies have explored whether the relationship between alcohol and breast cancer varies by type of breast cancer (ductal or lobular). Ductal carcinomas account for roughly 70% of invasive breast cancers in the United States, and lobular carcinomas account for 15%-20% of invasive breast cancers.
To assess the relationship between alcohol and type of breast cancer, researchers evaluated information from the Women’s Health Initiative (WHI) Observational Study. Among more than 87,000 postmenopausal women enrolled in the study, 2,944 developed breast cancer during follow-up.
Information about alcohol intake was collected by questionnaire at the time of study enrollment.
An important limitation of the study is that information about alcohol intake was collected only at the time of study enrollment. The analysis did not account for changes in alcohol intake that may have occurred after study enrollment.
The researchers conclude “Although one of the well-known risks of alcohol is an increased risk of breast cancer, this study suggests that alcohol primarily increases risk of lobular and hormone receptor-positive breast cancer.”
 Collaborative Group on Hormonal Factors in Breast Cancer. Alcohol, tobacco and breast cancer – collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 without the disease. British Journal of Cancer. 2002;87:1234-1245.
 Key J, Hodgson S, Omar RZ et al. Meta-analysis of alcohol and breast cancer with consideration of the methodological issues. Cancer Causes & Control. 2006;17:759-70.
 Li C, Chlebowski RT, Freiberg M et al. Alcohol consumption and risk of postmenopausal breast cancer by subtype: the Women’s Health Initiative Observational Study. Journal of the National Cancer Institute. Early online publication August 23, 2010.