Hello,

• Some types of cancer run in certain families, but most cancers are not clearly linked to the genes we inherit from our parents. Gene changes that start in a single cell over the course of a person's life cause most cancers. In this section you can learn more about the complex links between genes and cancer.
• Advances in genetics and molecular biology have improved our knowledge of the inner workings of cells, the basic building blocks of the body. Here we review how cells can change during a person’s life to become cancer, how certain types of changes can build on inherited gene changes to speed up the development of cancer, and how this information can help us better prevent and treat cancer.
• Cancer is such a common disease that it is no surprise that many families have at least a few members who have had cancer. Sometimes, certain types of cancer seem to run in some families. But only a small portion of all cancers are inherited. This document focuses on those cancers.
• Genetic testing can be useful for people with certain types of cancer that seem to run in their families, but these tests aren't recommended for everyone. Here we offer basic information to help you understand what genetic testing is and how it is used in cancer.

* Cancer is a genetic disease —that is, cancer is caused by certain changes to genes that control the way our cells function, especially how they grow and divide.

• Genes carry the instructions to make proteins, which do much of the work in our cells. Certain gene changes can cause cells to evade normal growth controls and become cancer. For example, some cancer-causing gene changes increase production of a protein that makes cells grow. Others result in the production of a misshapen, and therefore nonfunctional, form of a protein that normally repairs cellular damage.
• Genetic changes that promote cancer can be inherited from our parents if the changes are present in germ cells, which are the reproductive cells of the body (eggs and sperm). Such changes, called germline changes, are found in every cell of the offspring.
• Cancer-causing genetic changes can also be acquired during one’s lifetime, as the result of errors that occur as cells divide or from exposure to carcinogenic substances that damage DNA, such as certain chemicals in tobacco smoke, and radiation, such as ultraviolet rays from the sun. Genetic changes that occur after conception are called somatic (or acquired) changes.
• There are many different kinds of DNA changes. Some changes affect just one unit of DNA, called a nucleotide. One nucleotide may be replaced by another, or it may be missing entirely. Other changes involve larger stretches of DNA and may include rearrangements, deletions, or duplications of long stretches of DNA.
• Sometimes the changes are not in the actual sequence of DNA. For example, the addition or removal of chemical marks, called epigenetic modifications, on DNA can influence  whether the gene is “expressed”—that is, whether and how much messenger RNA is produced. (Messenger RNA in turn is translated to produce the proteins encoded by the DNA.)
• In general, cancer cells have more genetic changes than normal cells. But each person’s cancer has a unique combination of genetic alterations. Some of these changes may be the result of cancer, rather than the cause. As the cancer continues to grow, additional changes will occur. Even within the same tumor, cancer cells may have different genetic changes.
• Inherited genetic mutations play a major role in about 5 to 10 percent of all cancers. Researchers have associated mutations in specific genes with more than 50 hereditary cancer syndromes, which are disorders that may predispose individuals to developing certain cancers.
• Genetic tests for hereditary cancer syndromes can tell whether a person from a family that shows signs of such a syndrome has one of these mutations. These tests can also show whether family members without obvious disease have inherited the same mutation as a family member who carries a cancer-associated mutation.
• Many experts recommend that genetic testing for cancer risk be considered when someone has a personal or family history that suggests an inherited cancer risk condition, as long as the test results can be adequately interpreted (that is, they can clearly tell whether a specific genetic change is present or absent) and when the results provide information that will help guide a person’s future medical care.
• Cancers that are not caused by inherited genetic mutations can sometimes appear to “run in families.” For example, a shared environment or lifestyle, such as tobacco use, can cause similar cancers to develop among family members. However, certain patterns in a family—such as the types of cancer that develop, other non-cancer conditions that are seen, and the ages at which cancer develops—may suggest the presence of a hereditary cancer syndrome.
• Even if a cancer-predisposing mutation is present in a family, not everyone who inherits the mutation will necessarily develop cancer.

* By above explanation, Cancer is not a Congenital disease but its a most common human genetic disease. The transition from a normal cell to a malignant cancer is driven by changes to a cell’s DNA, also known as mutations.

* Hope this information helps !!

Dear Student,

cancer is not a congenital disease. Congenital diseases are diseases wherein structural or functional anomalies that occur during intrauterine life also know as birth defects, congenital disorders, or congenital malformations, these conditions develop prenatally and may be identified before or at birth, or later in life.

Some examples are, Fragile X syndrome, down syndrome etc.