Cancers develop usually by damage to the DNA or by genetic predisposition. With concern to the pathophysiology of cancers or malignancies by genetic predisposition; the two hit hypothesis explains how inherited traits lead to cancer development. The first hit is the inherited susceptibility gene wherein alone, will not cause cancer development. The second hit is usually caused by DNA damage brought about environmental factors (i.e. carcinogens). When the two hits are present, there will be cancer development. This hypothesis usually apply to the mutations in tumor suppressor genes rather than oncogenes (genes that promotes cancer development when activated).
