Margins in head and neck non-melanoma skin cancer surgery: clinical/pathological criteria and their impact on oncological outcomes and therapeutic choices. A systematic review.

Introduction: Non-melanoma skin cancers (NMSCs), including basal (BCC) and squamous cell carcinoma (SCC), are the most prevalent malignancies affecting the skin, with the head and neck region being the most common site of involvement. Surgical excision remains the primary treatment modality. The role of surgical margins in the treatment of skin SCC and BCC of the head and neck remains a subject of ongoing debate. Clear definitions and guidelines regarding adequate surgical margins, as well as their impact on recurrence rates and overall outcomes, are critical for improving clinical management. This systematic review aims to evaluate the current literature on the definitions of surgical margins for SCC and BCC of the head and neck, as well as their impact on local recurrence, disease free survival, and other patient-centred outcomes. Materials and methods: We conducted a systematic review following the PRISMA guidelines. A comprehensive search was performed across multiple databases, including PubMed and Scopus, for studies published up to December 2024. Eligible studies included those that reported on surgical margin definitions, surgical outcomes, and recurrence rates for SCC and BCC of the skin in the head and neck region. Data were extracted and analysed for margin size and oncological outcomes. Results: Following the application of inclusion and exclusion criteria, 30 studies have been retrieved for qualitative synthesis. Of these, 12 studies focused on SCC only, 14 on BCC only, and 4 on mixed histologies. Margin involvement rates ranged widely across the studies included (5-56%) as did thelocal recurrence rate (0-20%). This is associated with a variability of the surgical margin both for SCC and BCC, and of the definition of margin as close/negative at final pathology. Most studies do not define a threshold for close vs. negative margins at final pathology. All studies but one reported a significant correlation between positive margins and oncological outcomes, with particular regards to local recurrence. Conclusions: The findings highlight a lack of consensus on the optimal surgical margins for SCC and BCC of the head and neck, suggesting that margins may need to be individualised based on tumour characteristics, location, and patient factors. In particular, the anatomical complexity of the head and neck region suggests to separately address different high-risk areas as nose/midface, periauricular, and periocular with specific recommendations also concerning clinical margins.