[Encapsulated neuroma of the skin. A clinical, histologic and immunohistologic study]

Encapsulated neuroma of the skin is a little known, though not especially rare, benign tumour of the peripheral nerve system. It is often wrongly diagnosed on the basis of both clinical and histological investigation. We have subjected 24 encapsulated neuromas to clinical, histological, and immunohistological study. Clinically, they presented as solitary, skin-coloured small nodules, usually located on the face in middle-aged adults. Histologically, encapsulated neuromas are well-circumscribed dermal tumours. They are composed of interlacing fascicles of Schwann cells (S-100 protein +) and numerous tiny axons (S-100 protein +, neurofilament +). Most reveal at least partial encapsulation with perineurial differentiation (EMA +, vimentin +). Encapsulated neuromas can be differentiated from other tumours of the peripheral nerve system and from leiomyoma by their distinctive histological and immunohistological features.