Using p63 immunohistochemistry during Mohs micrographic surgery for cutaneous squamous cell carcinoma

Summary: Abstract Body: Background: Immunohistochemical (IHC) stains are increasing in use during Mohs micrographic surgery (MMS) when treating high-risk cutaneous squamous cell carcinoma (cSCC). This case series sought to understand the benefits of intraoperative p63 IHC stains during MMS for poorly differentiated cSCC. Methods: Intraoperatively, a staining protocol for AE1/AE3 and p63 IHC staining was implemented for 15 cSCC cases. One additional case used only p63 IHC staining. Stains were reviewed and graded by the Mohs surgeon as either minimal/no staining or strong straining. Results: Upon review, no p63 cases stained strongly for eccrine duct or follicular structures, compared to 67% of AE1/AE3 cases. Additionally, 89% and 50% of cases strongly stained tumor cells with p63 and AE1/AE3, respectively. After a mean follow-up time of 12 months, there have been two local recurrences and two deaths to date. Both deceased patients died of causes unrelated to cSCC. Conclusion: Intraoperative IHC with p63 during MMS for cSCC has not been previously explored in literature. We demonstrate the successful use of p63 IHC in combination with AE1/AE3 IHC in 15 cases with cSCC. The strong staining of adnexal tissue with AE1/AE3 can be visually distracting. IHC with p63 is promising considering the high rate of positivity in cSCC, more intense staining, and minimal staining of adnexal tissue. Interestingly, one case did stain more intensely for AE1/AE3 which is why we continue to use the stains in combination. While larger studies are needed, intraoperative p63 IHC staining in combination with AE1/AE3 IHC staining during MMS is likely beneficial in identifying poorly differentiated cSCC. Ella Engels², Kathleen Mannava¹, Tonya Woodard¹, Franki Lambert Smith¹ 1. Department of Dermatology, University of Rochester Medical Center, Rochester, NY, United States. 2. University of Rochester School of Medicine and Dentistry, Rochester, NY, United States. Clinical Research: Interventional Research