Excision is the surgical removal of a small amount of tissue or growth on the skin, such as an abscess or cyst, or in other parts of the body for treatment or testing, such as to diagnose a disease like cancer and to stage it.
Biopsy is the removal of tissue specifically to test it in the laboratory to confirm the type and severity of disease. Samples are looked at under a microscope to determine abnormalities in the cells. There are many different ways of collecting tissue for testing, depending on the location. The doctor may use small tools or a microscope or the procedure may need to be done in the operating room.