Mohs surgery removes less healthy tissue than excisional skin surgery. The Mohs surgeon cleans and numbs the area of skin to be operated on. Then he or she removes the visible portion of the tumor and a very small margin of healthy skin. The Mohs surgeon examines the tissue under a microscope for cancer cells. If part of the tumor is still present, the Mohs surgeon carefully maps out the area where the tumor remains and only removes additional skin in the area where the margin shows the tumor. The process is repeated until the tumor is completely removed. This type of surgery is typically reserved for melanomas on the face where it is beneficial to conserve as much healthy skin as possible during surgery.