Calcium Hydroxylapatite Tissue Filler Discovered 6 Years after Implantation into the Nasolabial Fold

Abstract

Injectable calcium hydroxylapatite is becoming increasingly popular as a facial soft tissue filler, due in part to its purported longevity of esthetic correction compared with other materials, but little is known about its long-term histologic appearance and persistence in facial skin. We recently encountered calcium hydroxylapatite microspheres incidentally during Mohs surgery of the nasolabial fold 6 years after implantation. To describe the long-term histologic appearance of calcium hydroxylapatite microspheres in human facial skin and review the relevant literature with a consideration of clinical implications. Routine hematoxylin and eosin staining was performed on frozen and fixed excised tissue containing calcium hydroxylapatite microspheres. Additional fixed sections were stained using Movat's pentachrome method. Numerous 4- to 20-mum round vacuoles were present throughout the reticular dermis associated with focal fibrosis, interstitial mucin, and little surrounding inflammation. Calcium hydroxylapatite microspheres and associated fibrosis may persist in facial dermis at least 6 years after implantation, long after its clinical effects are thought to subside. Dermatologists and dermatopathologists must be mindful of dermal implants because it is likely that incidental encounters will be an increasingly common occurrence.