Which of the following is a risk factor for breast cancer?

A family history of breast cancer is indeed a significant risk factor for developing the disease. Genetics play a crucial role in breast cancer susceptibility, as certain inherited mutations, particularly in the BRCA1 and BRCA2 genes, can greatly increase an individual's risk. When breast cancer is present in close relatives, such as a mother, sister, or daughter, it may indicate a hereditary pattern that could heighten risk for other family members.

In addition to genetic predisposition, family history may point to shared environmental factors or lifestyle choices that are common in that family. Thus, understanding an individual's family medical history is crucial for assessing overall risk and determining appropriate screening strategies. This underlines the importance of thorough family history-taking during patient evaluations in a clinical setting.

While a sedentary lifestyle, high-fat diet, and smoking can contribute to overall health and may be associated with increased cancer risks, they are not the primary risk factors like family history. Family history has a more defined link to breast cancer incidence and risk evaluation in clinical practice.