Giant Pigmented Tumor of the Scalp: A Diffuse Neurofibroma or a Congenital Nevus with Neurofibromatous Changes? Immunohistochemical and Electron Microscopic Studies

The document reported a case of a giant pigmented tumor on the scalp of a 47-year-old woman, characterized by a two-layered structure with an upper non-pigmented and a lower pigmented portion. Histological analysis revealed neurofibromatous tumor cells and naevus-like cells with melanin pigment. Immunohistochemical studies showed the presence of S-100 protein and neuron-specific enolase, but not neurofilament or myelin basic protein. Electron microscopy identified melanosomes in the pigmented portion, suggesting a melanocytic origin. However, the absence of superficial pigmentation and associated hair loss contradicted this, indicating a possible duality of neural crest differentiation.