DS21 Filler or foe: persistent hyaluronic acid filler encountered during Mohs micrographic surgery

Abstract

Hyaluronic acid fillers (HAFs) such as ‘Juvéderm’ are widely used in cosmetic facial augmentation. Although they are marketed as temporary, crosslinked HAFs may persist for several years and are sometimes incidentally encountered during Mohs micrographic surgery (MMS), potentially complicating tumour margin assessment. We report a case of persistent HAF identified during MMS for basal cell carcinoma (BCC), and highlight the importance of recognizing HAFs on Mohs slides. A 73-year-old patient presented with a 3-year history of a nonhealing lesion on the right angle of the mandible clinically and dermoscopically consistent with BCC. Scoop biopsy confirmed a mixed nodular and infiltrative growth pattern. MMS was performed for a 14 × 10-mm tumour, with margin assessment using haematoxylin and eosin (H&E) and toluidine blue staining. Representative high-quality digitized Mohs pathology slides were subsequently generated. Tumour clearance was achieved in a single Mohs stage, resulting in a 30 × 23-mm surgical defect, which was reconstructed with a direct side-to-side closure. Histological examination demonstrated well-circumscribed, nongranulomatous amorphous exogenous material within the subcutaneous fat. This material was readily identifiable on H&E-stained sections and exhibited marked metachromasia on toluidine blue staining. Further history confirmed cosmetic injection of ‘Juvéderm’ > 2 years previously, with additional treatments several years earlier. After consensus review with a consultant histopathologist, HAF material was concluded to be morphologically distinct from residual infiltrative BCC, avoiding further Mohs stages. This case reinforces evidence that cosmetic HAFs may persist for several years and be encountered during MMS. Recognition of their characteristic histological features is essential to distinguish filler from tumour, particularly infiltrative BCC, and to prevent unnecessary additional Mohs stages. Digitized Mohs slides provide a valuable educational adjunct, enabling clear comparison between H&E and toluidine blue staining. With increasing prevalence of cosmetic filler use, clinician awareness and thorough procedural history taking are increasingly important.