Efficacy of photodynamic diagnosis-guided Mohs micrographic surgery in primary squamous cell carcinoma.

Background: Cutaneous squamous cell carcinoma (cSCC) usually has ill-defined margins because of its irregular invasive patterns.

Objective: To evaluate the surgical efficacy of photodynamic diagnosis (PDD) in primary cSCC treated using Mohs micrographic surgery (MMS).

Methods & Materials: We examined 67 cases of biopsy-proven primary facial cSCC treated with MMS. The 67 SCC were divided into the two groups depending on PDD application: PDD group (n = 38, 56.7%) and non-PDD group (n = 29, 43.3%). We analyzed the differences in surgical features between the PDD and non-PDD groups.

Results: The PDD group required fewer Mohs stages (1.37 vs 1.83, p = .02) and smaller surgical margins (8.03 vs 11.24 mm, p = .03). PDD showed additional benefits in terms of surgical margin and Mohs stage, especially in low-risk SCC, including thin (≤4 mm), small (≤20 mm), well-differentiated, and nonulcerative tumors (p < .05) but did not show beneficial effects in high-risk SCC (p > .05) during MMS.

Conclusion: PDD can increase surgical efficacy of primary cSCC during MMS. These benefits are more pronounced in low-risk SCC. We recommend PDD as a simple and useful technique for delineating the margins of low-risk SCC before MMS.