Pathological Sampling of Basal Cell Carcinoma Re-excision Specimens: How Much is Enough?

Basal cell carcinoma (BCC) is the most common cutaneous malignancy, comprising approximately 75%-80% of all skin cancers. Surgical excision is the most common first line treatment modality, with the intent of obtaining clear margins. If the initial excision is incomplete or inadequate, a re-excision will often be performed in an attempt to achieve histological clearance. The pathological examination of these specimens requires a balance between the need for adequate assessment and efficient use of laboratory resources. In this study, we sought to systematically compare different approaches to the pathological sampling of these specimens in the hope of providing an evidential basis for a rational approach. Seventy-four BCC re-excision specimens were entirely sampled and retrospectively examined to determine the rate of detection of residual BCC which would have been achieved using different sampling methodologies. Residual BCC was identified in 37 specimens (50%). Limited transverse sections through the centre of the ellipse resulted in a sensitivity for detection of residual BCC of 78% (or 85% if only "significant" residual tumor is considered). By including the entire scar or the remainder of the specimen except the polar pieces, the sensitivity improved to 95% and 97%, respectively. Only one case showed residual tumor in the apical sections alone, with tumor extending to the new surgical margin in that case. We hope that this data may help laboratories develop sampling protocols appropriate to their own cost-benefit analyses and patient populations.