BCCs can arise in any area of the skin,
affecting the face, neck and upper trunk more often than the abdomen, lower
trunk and extremities. The areas around the eyes, the nose, the cheek bones and
the upper lip are the most frequently afected sites on the face. Usually only a
few become aggressive, when they are locally invasive and behave like ordinary
BCCs.
Evidence of aggressive transformation of
an individual lesion includes an increase in size, ulceration, bleeding, or
crusting. Some patients can develop aggressive BCCs without first developing
naevi.