Abstract: The present invention is a marker delivery device designed to deliver an elongated magnet to mark the center of tissue that is suspected of being cancerous. This device has an elongated magnet situated within a hollow needle with the magnet's distal end placed at the distal end of the needle. The operator first places the tip of the needle at the center of the lesion. By pressing an activate button on the injector device, the needle is advanced by half the length of the magnet and then pulled back the full length of the magnet while a rod within the needle that is in contact with the proximal end of the magnet prevents the magnet from coming back when the needle goes back. Thus the magnet is deployed with its center at the center of the lesion that is suspected of being cancerous.