Cancer surgery is usually the mainstay of the treatment of many types of cancers, particularly solid tumors of the body. Cancer surgery was one of the first treatments provided to cancer patients.
One article out of the American Cancer Society (1) discussed cancer surgery and how it works. It indicated that there are several reasons why cancer surgery is performed and that it is not always used to cure cancer.
Cancer surgery can be used to diagnose cancer (this is usually called a biopsy), to stage cancer (to tell how far the surgery has progressed), to cure the cancer (this means to remove the entirety of the cancer, to de-bulk the tumor (to remove the most of the tumor but not all of it), supportive surgery (to help the patient better receive other treatments for cancer), preventative surgery (to prevent a cancer from occurring in high-risk patients), reconstructive surgery (to help the body look better after cancer treatment), and for palliative reasons (to reduce the pain and other symptoms associated with cancer).
Source: 1.Cancer surgery. http://www.cancer.org/treatment/treatmentsandsideeffects/treatmenttypes/surgery/surgery-treatment-toc. Accessed 8/26/16.