An excision is a surgical procedure that is performed to remove an area of abnormal tissue from the body. Most are performed with the intention of removing most or all of the abnormal tissue from the patient in one procedure. The tissue is then sent to a pathologist who examines it under the microscope.
In many cases, a smaller surgical procedure called a biopsy has already been performed on the same site. The diagnosis reported after an excision often contains more information than the diagnosis performed after a biopsy because an excision provides the pathologist with more tissue to examine under the microscope.
For example, a patient may be diagnosed with breast cancer after a biopsy of a lump in her breast. After an excision removes the entire lump, the diagnosis will also include the size of the tumour which is required for providing a cancer stage.