Delayed Histiocytic Foreign Body Reaction and Granuloma Formation Following Argiform Injection for Soft Tissue Augmentation Mimicking a Lipomatous Tumor on Histopathology: A Case Report

As cosmetic procedures gain popularity, the use of nonapproved soft‐tissue fillers by unlicensed or untrained practitioners in nonmedical settings is rising. We report a rare case of a histiocytic reaction to foreign material following Argiform injection. A 31‐year‐old female presented with a 2 year history of an itchy and painful rash on both buttocks. The rash was initially confined to the right buttock but extended to the left several months later; it remained refractory to topical ointments. A skin punch biopsy revealed extensive adipocytic‐like cells within the dermis, some of which mimicked lipoblasts. Immunohistochemistry showed the lesional cells were positive for CD68 and negative for S100 and pancytokeratin. A final diagnosis of a histiocytic reaction to foreign material was made. Following the biopsy results, the patient disclosed a history of cosmetic Argiform injections at a spa 4‐5 years prior to presentation. This case demonstrates that delayed tissue reactions to Argiform can mimic lipomatous tumors, creating a significant diagnostic pitfall. Clinicopathologic correlation, including a thorough remote medical history, is critical for achieving an accurate diagnosis.