Spontaneous Regression of Congenital Melanocytic Nevi without Evidence of the Halo Phenomenon

Spontaneous regression of a congenital melanocytic nevus is rare and has always been thought to be associated with a halo phenomenon, suggesting that an immunological mechanism is involved in the regression process. We describe herein 2 cases of complete congenital melanocytic nevus regression without the halo phenomenon in 2 Japanese girls. To our knowledge, such a clinical progression has not been previously reported. We will also discuss several different possible mechanisms of regression.