When people hear the word “mutation,” they often think it automatically means cancer. In reality, mutations are simply changes in DNA, and they are a normal part of biology. Some mutations are harmless, some can increase cancer risk, and some directly drive cancer growth. A key point in understanding cancer genetics is knowing that there are two main categories of mutations: inherited mutations and acquired mutations. These two types differ in where they come from, what they mean for your health, and what they mean for your family.
Inherited mutations, also called germline mutations, are DNA changes that a person is born with. They are present in the egg or sperm and therefore exist in nearly every cell of the body from birth. Because they are part of the genetic material passed through generations, they can run in families. An inherited mutation does not mean a person will definitely develop cancer, but it can increase the likelihood of developing certain cancers and sometimes at younger ages than usual. Some inherited mutations affect genes that normally protect the body from cancer, such as genes involved in DNA repair or controlling cell growth. When these protective systems are weakened, the risk of cells becoming cancerous over time can rise. This is why inherited mutations are often linked to what doctors call hereditary cancer syndromes.
Acquired mutations, also called somatic mutations, are different because they are not present at birth. Instead, they develop over a person’s lifetime in specific cells. These mutations can occur naturally as cells divide and DNA is copied, or they can be influenced by environmental exposures such as tobacco smoke, ultraviolet radiation from sunlight, certain infections, chronic inflammation, or even aging itself. Acquired mutations are found only in the cancer cells (and sometimes in a small region of tissue around the cancer), not throughout the entire body. This is why they are not usually passed on to children. Most cancers arise primarily due to acquired mutations, which build up over time until a cell gains the ability to grow uncontrollably, avoid normal cell death, and spread.
Understanding whether a mutation is inherited or acquired is important because it changes the focus of testing and treatment. When doctors test a tumor, they are often looking for acquired mutations that are driving the cancer. These tumor mutations can sometimes guide targeted therapies, which are treatments designed to block specific genetic changes that cancer cells rely on to survive. On the other hand, when doctors suspect an inherited cancer risk, they may recommend germline genetic testing using a blood or saliva sample. Germline testing is especially relevant when there is a strong family history of cancer, cancers occurring at young ages, multiple cancers in the same person, or specific cancer types that are known to be linked to hereditary risk.
It is also possible for both processes to overlap. A person may inherit a mutation that increases susceptibility, and later in life their cells may acquire additional mutations that ultimately lead to cancer. In this situation, the inherited mutation creates a higher baseline risk, while acquired mutations act as the final triggers that allow cancer to form. This is why hereditary risk does not guarantee cancer, and why lifestyle factors, screening, and early detection remain important even when genetics plays a role.
From a broader perspective, whole genome sequencing of apparently normal individuals may be beneficial because cancer predisposition is often silent until disease develops. By identifying inherited risk variants early, even in people without symptoms, genome sequencing can help individuals and clinicians make informed decisions about screening intensity, timing, and prevention strategies. It can also uncover risk patterns that family history alone may miss, particularly in small families, families with limited medical records, or when risk is inherited from a parent who did not develop cancer. As genomic knowledge continues to grow, proactive sequencing could shift cancer care from reacting to disease toward anticipating risk and preventing cancer earlier, when outcomes are far more favorable.
