Why can a somatic mutation contribute to cancer without being inherited?

A somatic mutation contributes to cancer without being inherited because it occurs in a body cell rather than in the germ line (sperm or egg cells). While germinal mutations are passed to offspring, somatic mutations are acquired by a cell during an individual's lifetime due to factors like environmental exposure or errors during DNA replication.12

These mutations are transmitted only to the progeny of the mutated cell through cell division. Because they are confined to somatic tissues, they do not affect the genetic makeup of an individual's reproductive cells and therefore cannot be inherited by their children.12

In the context of cancer, these acquired alterations can deregulate normal cell growth, disrupt DNA repair mechanisms, or activate oncogenes. When these mutations accumulate in a specific cell lineage, they can lead to the uncontrolled proliferation and metastasis characteristic of cancer. While some individuals may inherit a predisposition to cancer, the majority of cases are sporadic, arising from these de novo somatic mutations that occur independently of family history.32