An increased incidence of breast cancer is associated with which factor?

• A. Nulliparity
• B. Late menarche
• C. Trauma to the breast
• D. Early natural menopause

Answer: (A)

Longer lifetime exposure to estrogen increases breast cancer risk, because estrogen stimulates breast cell proliferation over time. When a woman has no full-term pregnancies (nulliparity), she often experiences more menstrual cycles across her life, leading to more estrogen exposure. A full-term pregnancy provides protective changes in breast tissue and reduces the overall number of ovulatory cycles, which lowers risk. That makes nulliparity the factor most clearly associated with increased breast cancer incidence. By contrast, late onset of menstruation would cut estrogen exposure, while early natural menopause also shortens estrogen exposure, both reducing risk. Trauma to the breast is not a recognized risk factor for breast cancer.