Glossary — G

A gene mutation is a change in the sequence of DNA that makes up a gene, altering or disrupting the instructions that gene carries. Mutations can be inherited from a parent, arise spontaneously during cell division, or be triggered by environmental factors. In cancer biology, mutations that disable tumor-suppressor genes or activate growth-promoting genes are a central driver of malignancy.

Genetic counseling is a process in which a trained specialist — a genetic counselor — helps you understand genetic information relevant to your health, including what a test can and cannot tell you, how to interpret results, and what your options are once results are known. It is typically offered before and after genetic testing for inherited cancer risk.

Genetic testing examines your DNA — usually from a blood or saliva sample — to look for specific changes (mutations) in genes that are associated with inherited conditions or elevated disease risk. In cancer care, it is most commonly used to identify mutations in genes like BRCA1, BRCA2, and others linked to hereditary breast, ovarian, and colorectal cancer syndromes.

In oncology, grade describes how much cancer cells differ from normal, healthy cells when examined under a microscope. Low-grade (well-differentiated) tumors look relatively similar to normal tissue and tend to grow slowly; high-grade (poorly differentiated) tumors look very abnormal and tend to grow and spread more aggressively. Grade is distinct from stage, which describes how far a cancer has spread.