DS03: Tissue processing in Mohs micrographic surgery: what is current UK practice?

R. Jerrom and S. Varma

Nottingham University Hospitals NHS Trust, Nottingham, UK

Ever since Frederic Mohs described Mohs surgery in the 1930s the technique has evolved considerably. Previous literature has highlighted significant variation in Mohs tissue processing across the UK and concluded a need to share and standardize efficient practices. Having recently reviewed and changed the way we process Mohs specimens in our centre we sought to discover what the current practice is across the UK for tissue processing in Mohs. In January 2021 we circulated a Survey Monkey questionnaire, consisting of 10 questions related to Mohs tissue processing and slide interpretation, to all members of the British Society for Dermatological Surgery (BSDS). The survey was completed by 44 of 98 registered Mohs surgeon members of the BSDS. Of these respondents 39 are currently practising Mohs surgery, equating to a 40% response rate. It appears that single-section Mohs processing is now the predominant approach, with 60% reporting this as their primary practice and only 35% preferring to divide specimens in the conventional way. Five per cent reported their preference as ‘other’. Sixty-seven per cent of respondents report using a glass slide-embedding technique, with 33% of these using their own locally developed rig to achieve this. However, most respondents (62%) do not feel confident in their own ability to embed tissue and 78% reported that embedding was primarily performed by biomedical scientists/laboratory technicians in their departments. Reporting of the estimation of tissue cutting to achieve full face was varied and ranged from < 100 to 800 microns, but 59% reported that they achieve full face within 200 microns, of whom 73% were using the glass slide technique to achieve this. The thickness of sections varied, but > 97% of respondents section tissue at ≤ 10 microns, with 45% of these cutting < 8 microns. The most popular distance between sections was 100–200 microns, reported by 55%, but 40% cut sections at intervals < 100 microns. Histological interpretation is performed by 83% of the Mohs surgeons alone, with a further 12% reading the histology alongside a histopathologist and 5% reporting that they do not interpret the slides at all. The 44 members’ replies provide valuable information, although it is possible that the remaining 54 members have other approaches. Significant variation in Mohs practice across the UK is still suggested by the data. It appears that Mohs surgeons are transitioning away from the traditional approach of dividing specimens and now prefer to process single sections, with a glass slide-embedding technique the most popular approach. Having recently switched to these techniques locally, with clear improvements in slide quality and significant gains in efficiency, we believe that these trends will continue.