Why do basal cell carcinomas recur (or not recur) following treatment?

There seem to be two types of recurrences of basal cell carcinoma ‐ those due to regrowth of residual tumor (residual tumor recurrence) and those due to growth of a new independent tumor (new tumor recurrence). Twelve examples of residual tumor recurrence and three of new tumor recurrence are briefly presented. Also two examples of nonrecurrence of basal cell carcinoma following incomplete surgical removal are outlined. False negative and false positive pathological reports occasionally occur, and some basal cell carcinomas may show residual tumor recurrence years after the primary treatment. These findings suggest that there is more to the treatment of certain basal cell carcinomas than wide local excision or local destruction.