Which factor is NOT associated with an increased risk of breast cancer?

The correct answer, indicating that trauma to the breast is not associated with an increased risk of breast cancer, aligns with the understanding of risk factors for the disease. Trauma, such as injuries or accidents leading to bruising or cuts to the breast tissue, has not been shown to elevate the risk of developing breast cancer. Research indicates that physical trauma does not lead to cellular mutations or other underlying changes in breast tissue that could predispose one to cancer.

In contrast, the other factors listed—nulliparity (not having children), late menarche (starting menstruation at a later age), and early natural menopause—are recognized as risk factors. Nulliparity can increase the risk because women who do not have children may have more menstrual cycles over their lifetime, which increases their exposure to estrogen. Late menarche extends the exposure to estrogen and progesterone, while early menopause reduces the protective effects these hormones can confer.

Understanding the nuances of these associations helps highlight why trauma does not play a role in breast cancer risk, making it a unique factor compared to the others listed.