DS16: Approach to superficial basal cell carcinoma when encountered in Mohs micrographic surgery: a UK national survey

B. Salence, Z. Askham, W. Perkins and S. Ziaj

Oxford University Hospitals NHS Foundation Trust, Oxford, UK

According to the 2020 UK Service guidance and standards for Mohs micrographic surgery (MMS), MMS should be considered for basal cell carcinoma (BCC) with aggressive histology and particularly for those in high-risk anatomical sites (the H zone). A Mohs surgeon may encounter the situation where the invasive component of a BCC (nodular, micronodular or infiltrative) is removed but the superficial component requires more stages to clear. This may lead to a significantly larger defect, resulting in a more complex reconstruction. We aimed to assess the variations in the surgical approach to superficial BCC when encountered in MMS through a nationally distributed survey to the members of the British Society for Dermatological Surgery in December 2021 over a 4-week period. Of the 96 Mohs surgeons in the UK, we received 31 responses (32% response rate). Fifty-five per cent of UK Mohs surgeons (n = 17) had more than 10 years’ experience, and most respondents performed more than 100 cases a year (n = 26; 84%). Photomicrographs of serial sections were used, demonstrating superficial BCC at the edge of a nodular BCC and infiltrative BCC. Most surgeons (n = 14; 45%) often chase the superficial component of a BCC on the nose once the original BCC is clear but do so on the basis of patient-specific factors. Three surgeons (10%) always chased the superficial component on the nose until clear when the original BCC (nodular/micronodular) was clear, but this increased when the original BCC was infiltrative (n = 8; 26%). Seven surgeons (23%) always only took one more Mohs layer to chase the superficial BCC component, whether the original tumour was infiltrative or nodular, with 6/7 (86%) having more than 10 years’ experience. Two surgeons (6%) chose an alternative treatment modality for the superficial component rather than MMS. If no further Mohs layers were taken, imiquimod 5% cream was the most prescribed adjuvant treatment for the superficial remnants of the original BCC (n = 14; 45%) with the majority recommending imiquimod 5% cream 3 months after MMS (n = 10; 71%) and used five times per week for 6 weeks (n = 7; 50%). BCC recurrence was seen by most surgeons following MMS when additional treatments had been used for the residual superficial disease (n = 22; 73%). Our survey highlights the need for consensus on the approach to superficial BCCs when encountered during MMS when the original BCC is cleared. We propose a national observational study/registry in order to evaluate the risk of recurrence and adjuvant treatments with MMS for high-risk BCCs with coexisting superficial disease.