Do plastic surgeons resect basal cell carcinomas too widely? A prospective study comparing surgical and histological margins.

Basal cell carcinoma is a common condition facing the plastic surgeon. When formally excised, a surrounding margin of normal skin is included in an attempt to ensure complete excision. We set out to investigate our excision margins in a prospective study of 100 basal cell carcinomas in 86 patients treated by conventional surgical excision. The edge of each lesion was delineated, an excision margin was drawn, and the closest point was identified and measured. The tumours were excised, and the specimens were examined to determine the closest histological margin. A comparison was made between the marked surgical margins and the margins observed on microscopy. The mean observed surgical margin was 3.0 mm and the mean histological margin was 3.7 mm; 44% of the margins agreed to within 1 mm, 79% to within 2 mm and 92% to within 3 mm. There were four incomplete excisions, all at the lateral margin. There was agreement in the position of the closest margin in 69% of cases. The measured surgical excision margins correlated well with those assessed histologically, as did the position of the closest margin. Given a 3 mm margin, 96% of lesions would have been excised completely. We feel that our current practice represents a satisfactory balance between maintaining a low rate of incomplete excision and minimising the sacrifice of normal skin.