Breast cancer Quiz: Ace Your Exams

A 70-year-old African-American woman, gravida 3 para 3, comes to the clinic due to a breast mass found on self-examination. She is generally healthy and does not smoke or use illicit drugs. She drinks 2-3 glasses of wine per week and 4-5 cups of coffee per day. Menarche was at age 12 and first pregnancy at age 22. Family history is significant for breast cancer in her maternal aunt at age 55. The patient’s father had colon cancer at age of 60. The patient has never been very physically active. Vitals are within normal limits. On physical examination, a fixed, palpable firm mass is noted in the left breast. Mammogram shows a suspicious mass with calcifications. Core needle biopsy is performed and confirms the diagnosis of ductal carcinoma in situ. While discussing treatment options, the patient asks the doctor why she developed this condition. Which of the following confers the most significant risk factor for the development of breast cancer in this patient?