Intraoperative tissue treatment methods are used following the removal of target tissue, e.g. diseased tissue, from a target site, e.g. within a patient's breast, leaving access to the target site. In one method an expandable element is introduced into and expanded within a void at the target site. If it is determined that all of the target tissue was not removed, then a layer of tissue at least partially surrounding the expanded element is removed from the patient, preferably in a substantially intact form, to permit inspection for evidence of the target tissue still within the patient. In a second method the suction inlet of a suction device is located so to be in fluid communication with the void. Fluid is then withdrawn through the suction inlet so to at least partially collapse the tissue defining the void. If it is determined that all of the target tissue has not been removed, at least a portion of the collapsed tissue is removed from the patient and analyzed for evidence of target tissue still within the patient. With a third method, the sheath is maintained along the passageway from the region external of the patient to the void at the target site. A flexible implant is passed through the sheath and into the void so to at least substantially fill the void. The sheath is then removed from the patient.