Most dermatologists and dermatopathologists use a system devised by the NIH for classifying melanocytic lesions. In this classification, a nevus can be defined as benign, having atypia, or being a melanoma. A benign nevus is read as (or understood as) having no cytologic or architectural atypia. An atypical mole is read as having architectural atypia, and having (mild, moderate, or severe) cytologic (melanocytic) atypia. Usually, cytologic atypia is of more important clinical concern than architectural atypia. Usually, moderate to severe cytologic atypia will require further excision to make sure that the surgical margin is completely clear of the lesion.