Definition

A laboratory method that looks for changes in genes, gene expression, or chromosomes in cells or tissue of a person. These changes may be a sign of a disease or condition, such as cancer. They may also be a sign that a person has an increased risk of developing a specific disease or condition or of having a child or other family member with the disease or condition. Genetic testing may also be done on tumor tissue to help diagnose cancer, plan treatment, or find out how well treatment is working.