Mohs micrographic surgery (MMS) is the gold standard for treatment of non-melanoma skin cancer (NMSC), offering high cure rates and precise margin control. A common postoperative complication in flap reconstruction is pincushioning, or the “trapdoor” phenomenon, caused by scar contraction and tissue edema. We present the case of a female patient who developed apparent pincushioning nine months after MMS for a perioral NMSC reconstructed with a local advancement flap. Prior to scar revision, clinical evaluation revealed a buccal (alveolar) exostosis—benign bony protuberances of the maxilla or mandible abnormalities—causing a pseudo-pincushion appearance in the patient. Recognition of this incidental finding prevented an unnecessary corrective procedure, highlighting the importance of thorough physical and oral examination and consideration of alternative diagnoses before undertaking revision treatments following MMS and reconstruction.

Maria Trung earned her Doctor of Medicine degree from Louisiana State University in 2025 and completed her preliminary internship at Tulane University in 2026. She is currently a dermatology resident at Louisiana State University. Her academic interests include Mohs micrographic surgery, cutaneous oncology, and cosmetic dermatology. She has authored multiple peer-reviewed publications in Dermatologic Surgery, the Journal of Clinical and Aesthetic Dermatology, and the International Journal of Dermatology.