Breast cancer has become a major public health problem in Latin America, as it is the most common form of cancer among women. Women are more likely to develop breast cancer at younger age, and to be diagnosed at an advanced stage compared to western women. Over the past twenty years, the mortality from breast cancer in Latin America has also been increasing very rapidly, and is currently the leading cause of cancer mortality. Little is known on specific risk factors for premenopausal breast cancer in general, and in Latin America in particular. There is a lack of specific knowledge on tumor molecular and pathological characteristics of breast cancer in Latin America premenopausal women, and this has major consequences on cancer treatment and survival.