Dermal melanocytic proliferation with features of a plaque-type blue nevus and neurocristic hamartoma

Abstract

Blue nevi (BN) and neurocristic hamartomas (NCH) are pigmented lesions that originate from the aberrant development of cells derived from the neural crest. BN are composed of dermal melanocytes, whereas NCH have a broader histology and show Schwann cell differentiation as well. In addition, BN and NCH might differ in their potential to develop into a malignancy. We describe a patient with a lesion showing features of both a plaque-type BN and NCH.

The dermal melanocytoses (DM) include a variety of pigmented lesions that are formed from the aberrant development of the neural crest–derived melanocytes as they migrate through the dermis during embryogenesis.1 (Table I) Characteristics, such as the distribution, morphology, and depth of the dermal melanocytes, degree of stromal alteration, and the size and location of the lesion, are all features that help to differentiate the various types of DM.2,3 (Table II) Some features of DM, such as lymph node involvement and extension along nerves and into muscles, can raise the concern for malignancy.4