LAUSR

SURGICAL CHALLENGE Facedwith a positive deep histologic margin, a common error is to focus the re-excision solely on achieving a depth greater than that of the first attempt. Viewing the wound from the surface, with the knowledge that the peripheral margins are negative, can lead to the misperception that the persistent tumor lies immediately deep to the scar line (Fig 1,A). However, the base of the original excision remains an ellipse despite the surface having been closed. Therefore, residual tumor may be present anywhere in the base of the defect, including abutting $1 peripheral margin (Figs 1, B and 2, A). Reopening the original wound and resecting just the base is also flawed. Tissue distortion caused by contracture and scarring make identifying the true base of the original excision unreliable. In addition, tumor cell transfer may have occurred between the defect base and adjacent tissue after wound closure.