A 40-year-old mother of two presents to your office for cons…

A 40-year-old mother of two presents to your office for consultation. She is interested in knowing what her relative risks are for developing breast cancer. She is concerned because her sister had unilateral breast cancer 6 years ago at age 38. The patient reports on her history that she began having periods at age 11 and has been fairly regular ever since, except during her two pregnancies. Her first child arrived when she was 26 and her second at age 28. Otherwise she has had no health problems. Her father has high blood pressure. Her mother had unilateral breast cancer in her 70s. The patient denies tobacco, alcohol, or drug use. She is a family law attorney and is married. Her examination is essentially unremarkable. Which risk factor of her personal and family history most puts her in danger of getting breast cancer?