Most frequently the Dermatologist can treat the patient without having to do a biopsy, but when a biopsy is performed it may be from any one of a wide range of lesions. The skin is our protection from the outside world, but we challenge it in so many ways: with things that produce allergic reactions, with fungal or viral infections, with too much sunshine, and of course with the passage of time. Sometimes the biopsy confirms the clinical diagnosis. In other times it will try to resolve a differential diagnosis.