A Retrospective Review of Histopathologic Features Associated with Increased Risk of Recurrence of Non-melanoma Skin Cancer After Mohs Micrographic Surgery.

Objective: Mohs micrographic surgery (MMS) is the gold standard treatment for non-melanoma skin cancer (NMSC). However, NMSC recurrence may occur in a small proportion of patients. The aim of this study was to identify histopathologic features seen on the final stage of previous MMS, which may increase the risk of NMSC recurrence. Methods: This was a single-institution retrospective study of 39 recurrent basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs), which were treated with MMS. Slides from the final stage of previous MMS were reviewed by two board-certified dermatopathologists for the following histopathologic features: perineural inflammation, dense inflammation, mucin, ruptured follicle, actinic keratosis, and missing tissue. Results: Twenty recurrent BCCs and 19 recurrent SCCs were included. Histopathologic features identified on the final stage of previous MMS included missing tissue from the epidermis, dermis, and/or subcutis (69%), actinic keratosis (51%), perineural inflammation (10%), and dense inflammation (8%). Ruptured follicle was present in one BCC case, and mucin was not identified in any cases. Limitations: Limitations include retrospective study design, small number of recurrent cases, single institution, and lack of a control group consisting of NMSC cases which did not recur after MMS. Conclusion: Mohs surgeons should carefully evaluate NMSC frozen sections for the presence of missing tissue, actinic keratosis, perineural inflammation, and dense inflammation as these histopathologic features may be associated with tumor recurrence. It is of paramount importance to acquire high quality frozen sections for thorough margin evaluation.