Classification of Acne Scars: Clinical and Instrumental Evaluation

Causes of acne scar formation can be broadly categorized as the result of increased tissue formation or, more commonly, loss or damage of local tissue. Clinical manifestations of acne scars and severity of scarring are generally related to the degree of inflammatory reaction, to tissue damage, and to time lapsed since the onset of tissue inflammation. In 1987, D. A. Ellis and M. J. Mitchell proposed an acne scar classification system and first utilized the descriptive terms ice pick, crater, undulation, tunnel, shallow-type, and hypertrophic scars. Acne scars in this system are classified as elevated, dystrophic, or depressed. Other parameters include shape, consistency, color, and distensibility. An accurate evaluation and classification of acne scars is crucial for the selection of the optimal therapeutic approach. Histopathologic examination, which may most precisely depict scar morphology, is not feasible in routine clinical practice, and non-invasive instrumental techniques could be useful for this purpose.