Delayed adverse reaction to a natural dermal filler mimicking salivary gland neoplasia.

Background: Cosmetic dermal fillers are a sought-after procedure globally. However, despite the safety claims of filler materials by the manufacturers, adverse reactions still occur. Case presentation: This case report is of a 66-year-old female who presented with a late-onset complication of a hyaluronic acid dermal filler that clinically mimicked a salivary gland neoplasm. The patient presented with firm peri-oral swellings of short duration that clinically mimicked a pleomorphic adenoma and mucoepidermoid carcinoma. The diagnosis was that of a foreign-body granulomatous response to dermal fillers. Although other mimics of a similar nature are reported a knowledgeable clinician, careful choice of filler material, knowledge of the product, thorough pre-procedural history taking and post-procedural patient follow-up can drastically minimize a possible misdiagnosis. The reaction was treated with a combination of hyaluronidase, betamethasone and 5-flurouracil intra-lesional injections monthly for 11 consecutive months, with total clinical resolution. Conclusions: Patient education of the procedure, product name and the possibility of an adverse reaction occurring, even years later or at a site distant to the initial site of placement, is vital. Further, we review the recent reported adverse association of the new mRNA COVID-19 vaccines and dermal filler placement.