Verocay body--prominent cutaneous schwannoma

We report on eight cases of a distinct variant of cutaneous schwannoma characterized by prominent Verocay body formation (75-100% of the tumor bulk) that may cause considerable diagnostic difficulties. Like ordinary cutaneous schwannomas, these lesions preferred the head and neck region of young adults without sexual predilection and were clinically interpreted as cyst, basal cell carcinoma, or nevus. Histological examination revealed well-circumscribed nodules. Three of them consisted exclusively of nodular or ribbon-like Verocay bodies. A variable admixture of Antoni A or B type of differentiation (< 25%) was seen in five other cases. The following patterns were seen: fascicular spindle-shaped, onion-like epithelioid, myxoid-hypocellular, and degenerated ("ancient") with prominent fibrosis/hyalinosis and occasional bizarre giant cells. Immunohistochemically, the lesions were positive for S-100 protein (and vimentin) but negative for a broad panel of neurogenic and intermediate filament markers. The capsule showed focal labeling for EMA and--when it was markedly thickened--also for SMA. Labeling with E9, an anti-metallothionein marker indicative of cell activity, was negative, underscoring the slow growth potential of these lesions. No recurrence was seen in the six patients with follow-up information. The differential diagnosis includes other lesions with prominent palisading. (Amianthoid) myofibroblastoma and palisading leiomyoma are consistently positive for SMA and desmin, respectively. Palisading cutaneous fibrous histiocytoma and myofibroblastic dermatofibroma are variably positive for Factor XIIIa, SMA, and E9 and/or NK1C3 (CD57). Palisaded encapsulated neuromas are primarilly differentiated by the presence of nerve fibers with myelin sheaths.