Treatment

Surgical excision is the standard treatment. Randomized trials of excision margins are
lacking, but generally margins of 2 mm (for well-circumscribed lesions, particularly on
the face) to 5 mm (for lesions with indistinct margins) are recommended. Four millimetre
margins give a cure rate of 94–96% according to Zitelli.
Some areas such as the medical canthus, and external auditory alar base meatus
are more prone to incomplete excision as the tumour seems to extend deeper at these
locations; the usual explanation being that these areas are embryological fusion lines.
Note that only one-third of incompletely excised BCCs will show histological evidence
of residual tumour on further resection. Recurrent lesions tend to be more
aggressive in behaviour.
Mohs’ micrographic surgery (MMS)—in which successive layers are exised and the
base of the specimen is mapped out and examined histologically perioperatively—
may be most useful in complex lesions with indistinct borders and where tissue conservation
is important. It has the best reported cure rate of 99%.