A system for at least partially filling and marking a cavity at a site within a patient's body includes a marker delivery device having a chamber configured to contain a marking substance and having a mechanism configured to expel the marking substance. A quantity of the marking substance is contained within the chamber of the marker delivery device. The marking substance is configured to at least partially fill the cavity and form therein a porous bioabsorbable body. A delivery tube is coupled in fluid communication with the chamber of the marker delivery device. The delivery tube has a distal end with a discharge port through which the marking substance is expelled. A marker is configured to be delivered to the cavity from the distal end of the delivery tube and is configured to remain with the porous bioabsorbable body within the cavity upon the formation thereof.