General Factors:

The most important risk factor in breast cancer is age. Other factors include sex, inherited genetic mutations (in BRCA1 & BRCA2 genes),  personal or family history of breast cancer, high breast tissue density, biopsy-confirmed hyperplasia, high-dose radiation to the chest as a result of medical procedures.

Physical Factors:

There are several physical factors that can contribute to the risk of developing breast cancer. Among these are reproductive history, menstrual history (mentral cycle that starts early and/or end late in life), never having children, use of oral contraceptive, late child-birthing (having first child after age 30).

Obesity:

Overweight or obesity after menopause
Adversely affects survival for postmenopausal women with breast cancer
Physical Inactivity
Postmenopausal Hormone Therapy

Social Factors:

Alcohol consumption
Alcohol consumption of one or more beverages per day
Environmental influences
Genetically engendered food