Abstract: A method and apparatus for localizing and excising masses which are not palpable in human tissue. A surgical needle is inserted into a located mass and encircled by a cork screw device which is twisted around the mass until the tip of the worm is just beyond the furthest side of the mass from the operator. Subsequently, the handle of the cork screw device is removed and replaced with a guiding extension rod which is used to direct the surgeon as to the depth of the mass in the patient's tissue. A cutting instrument having an inner cylinder and a hollow outer barrel attached to cutting jaws with knife edges is inserted over one end of the extension rod, with the jaws in an open position, and twisted around the worm of the cork screw into the patient's tissue. The cutting jaws of the instrument are opened by pushing finger flanges away from the surgeon causing the cutting jaws to pivot outwardly into an open position.