In general, surgery is the most commonly used treatment for cancers that form solid tumors. The primary goal of cancer surgery is to completely remove all detectable traces of tumor (or tumors), preferably with a margin of normal tissue surrounding all surfaces of the tumor(s).
In addition to the complete removal of primary tumors (and, in some cases, metastatic tumors as well), surgery is also often used to "stage" a patient's cancer. For many types of cancer, the surgeon not only attempts to remove all detectable deposits of tumor, but he/she also may remove lymph nodes in order to determine if cancer cells have already spread outside of the primary tumor. Staging of regional lymph nodes is routinely done for many types of cancer, including breast cancer, colorectal cancer, melanoma, lung cancer, stomach cancer, and most gynecologic cancers, among others.
As surgery is considered a "local-regional" therapy, many patients with cancer may also be advised to undergo chemotherapy, or other types of therapy that treat the entire body, in an effort to destroy microscopic deposits of cancer cells that the surgeon cannot see or feel.