CONCLUSIONSUltrasound and histologic observations confirm differencesin tissue behavior after subcutaneous injection of 2HA volumizers. Whether injected by needle bolus or cannularetrograde fanning technique, CPM gel appeared asa homogeneous pool of gel that only slightly diminishedin size after gentle massage. Vycross gel appeared moreheterogeneous and was less resistant to gentle massagewith a tendency to break up into smaller pools particularlyafter cannula injection. It was also associated with a morediffuse inflammatory reaction at day 21. The results suggestthat CPM gel maintained greater integrity after subcutaneousinjection and gentle massage.