Pseudo‐Pincushioning After Mohs Micrographic Surgery Due to Buccal (Alveolar) Exostosis

Mohs micrographic surgery (MMS) is the gold standard for treating non-melanoma skin cancer (NMSC), providing complete circumferential assessment of peripheral and deep margins and achieving cure rates of 97%–99% for the most common cutaneous malignancies [1]. Once tumor clearance is achieved, reconstruction becomes the next critical step. Local flaps and grafts are often employed when secondary intention or primary closure is not feasible [2]. However, advancement and transposition flaps may develop a postoperative complication known as pincushioning, or the “trapdoor” phenomenon, characterized by a raised, bulging appearance of the flap. This occurs due to scar contraction, redundant subcutaneous tissue, or lymphatic and venous obstruction [3]. Although mild cases often resolve spontaneously, persistent or cosmetically displeasing cases may require interventions such as scar revision, dermabrasion, laser therapy, or intralesional corticosteroids [4]. Here, we present a case of a patient with apparent persistent pincushioning 9 months following MMS and subsequent local advancement flap repair who was found to have an incidental buccal exostosis creating a pseudo-pincushion appearance. This case underscores the importance of a thorough intraoral examination before performing revisional procedures. A 51-year-old female presented to our MMS clinic for treatment of a basal cell carcinoma (BCC) located on the left upper cutaneous lip. Following tumor clearance, the defect was reconstructed using a local advancement flap (Figure 1A,B). The postoperative course was initially unremarkable; however, the patient noted lip fullness and bulging. At the time of suture removal, the potential for pincushioning was discussed but was managed conservatively with routine follow-up to monitor for spontaneous resolution. At 9 months postoperatively, the contour irregularity persisted, and scar revision and intralesional triamcinolone were offered (Figure 1C). However, on palpation, the upper lip was not thickened, and no scar hypertrophy or keloid was palpated. Upon a closer intraoral evaluation, a firm, non-tender submucosal mass was noted on the inner buccal gingival surface (Figure 1D). Further examination revealed a buccal exostosis, which was determined to be the source of the apparent pincushioning. Upon further questioning, the patient had been aware of the gingival protuberance for years prior to surgery. The patient was subsequently spared unnecessary intervention. The primary goals of MMS for NMSC are complete tumor removal and preservation of both function and aesthetics. Reconstruction of the perioral region poses unique challenges due to its central facial location and its essential role in speech and mastication. Common reconstructive options include secondary intention healing, linear closure, and local flaps—such as advancement, rotation, or transposition flaps—selected based on defect location, size, and cosmetic considerations [2]. While local flaps generally yield excellent cosmetic outcomes, complications such as pincushioning may occur due to flap contraction, edema, and scar hypertrophy [3]. Prevention strategies include ensuring tension-free closure and adequate defatting of the flap. Persistent pincushioning can be managed with defatting, scar revision, dermabrasion, laser resurfacing, or intralesional corticosteroids [4]. In this case, the patient's clinical pincushioning caused by an intraoral protrusion was secondary to a buccal exostosis—a benign bony protuberance of the maxilla or mandible, typically located near the premolar or molar region. The etiology of buccal exostoses remains unclear but may involve increased masticatory stress. They are generally asymptomatic and diagnosed clinically, with imaging used to confirm the diagnosis when needed. Treatment is typically only indicated if symptomatic or for prosthetic reasons [5]. In our case, recognition of this condition prevented an unnecessary surgical revision procedure. This case highlights the need for meticulous preoperative assessment, with careful inspection and palpation of the oral cavity in patients with lip tumors, thorough history taking and photographic documentation, and vigilance for alternative causes when evaluating postoperative contour irregularities. Identifying a buccal exostosis in this patient averted unnecessary intervention and underscores the value of comprehensive physical and intraoral examinations in dermatologic and reconstructive surgery, particularly of the lip. The authors have nothing to report. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.