What causes cancer according to molecular diagnostics?

Cancer is primarily the result of nonlethal mutations in DNA that lead to uncontrolled cell division and growth. These mutations can affect genes that regulate the cell cycle, apoptosis (programmed cell death), and DNA repair mechanisms, ultimately contributing to the development of cancerous tumors. Molecular diagnostics focuses on identifying these mutations, understanding their implications for cancer progression, and tailoring treatment strategies based on individual genetic profiles.

This understanding sets it apart from other factors listed in the options. While excessive physical activity can influence overall health and reduce cancer risk, it does not directly cause cancer. Similarly, although some infections with viruses can contribute to cancer development, the question specifically asks about molecular diagnostics, which emphasizes genetic mutations as the underlying cause. Environmental contaminants can be risk factors for cancer by causing DNA damage, but they are not intrinsic to the molecular mechanisms that lead to the disease as nonlethal mutations in DNA are.