How accurate is the visual assessment of basal carcinoma margins?

This study evaluated the accuracy of visual determination of tumour margins in basal cell carcinomas. Using a 2.5 × binocular magnifier, the apparent tumour margin was marked pre-operatively by light electrodesiccation. Following excision, the electrodesiccation mark was compared to the actual tumour edge by microscopy of step level sections. It was possible to delineate the tumour margins with an accuracy of 1 mm in 94% of a selected series of 101 basal cell carcinomas. These findings support the view that a 2 mm margin of normal tissue is adequate in the surgical treatment of most basal cell carcinomas.