The spectrum of neurocristic cutaneous hamartoma: clinicopathologic and immunohistochemical study of three cases.

Neurocristic cutaneous hamartomas result from aberrant development of the neuromesenchyme. Thus, the elements within these tumors reflect the spectrum of differentiation that results from migration of neural crest-derived cells. We present three cases, in addition to routine hematoxylin-eosin staining, a battery of immunohistochemical staining, including S-100 protein, HMB-45, EMA, CD34, and neurofilament-protein stains, was performed on each specimen. A dermal melanocytic component was the dominant feature of two of these lesions, while neurosusenticular and neuromesenchymal components dominated in one tumor. Both tumors that developed on the scalp showed effects on the overlying epidermis and/or on adnexal development. The melanocytic component was positive for S-100 protein and HMB-45. The surrounding stroma showed tactoid bodies and increased CD34 staining. Neurocristic cutaneous hamartomas represent dysplastic development of neural crest-derived cells. Although melanocytic cells have been previously reported to be the dominant cell population, neurosusentacular and neuromesenchymal cells also may be the principal component. In cephalic areas, the neuromesenchyme may not only be an important component of the tumor, but may also effect the development of the overlying epithelium and adnexal structures. Although none of these cases presents evidence of malignant transformation, identification of these tumors could be important if malignant transformation results in the development of tumors with a distinctive biologic behavior.