NEUROCRISTIC CUTANEOUS HAMARTOMA - A DISTINCTIVE DERMAL MELANOCYTOSISWITH AN UNKNOWN MALIGNANT POTENTIAL

Neurocristic hamartomas (NCHs) result from aberrant development of the neuromesenchyme. In addition to a dermal melanocytic component, these tumors can contain neurosustentacular and fibrogenic components and c an undergo malignant transformation. Although NCHs have many features in common with Other dermal melanocytic neoplasms, including cellular blue nevi and some congenital nevi, they have distinctive clinical and histologic features. We present a case report of a 27-year-old white woman with an NCH of the scalp. The clinical, histologic, and immunohi stochemical features are compared with those of other dermal melanocyt ic neoplasms. The NCH contained epithelioid pigmented melanocytes posi tive for S-100 and HMB45, within which there were well-circumscribed n odules of S-100+/Leu 7+/HMB45- cells surrounded by a capsule composed of spindle cells positive for epithelial membrane antigen. The stromal cells throughout the tumor were diffusely CD34 positive, and hair fol licles were decreased and dystrophic within the tumor. NCHs represent neoplastic dysplasia that involves not only melanocytic cells but also neurosustentacular and fibrocytic effector cells. The histologic and immunohistochemical features, along with the decreased and dystrophic hair follicles, suggest that the abnormalities in the mesenchyme are s ignificant and result from the contribution of neural crest cells to t he cellular and matrix components of the mesenchyme.