Melanotic Schwannoma of Bone: Clinicopathologic, Immunohistochemical, and Ultrastructural Features of a Rare Primary Bone Tumor

The authors report a 35-year-old woman who presented with a lytic and blastic tumor of the ilium with soft tissue extension. The resected tumor showed light microscopic and ultrastructural features characteristic of a melanotic schwannoma. An unusual histologic finding was the presence of laminated concretions resembling psammoma bodies. Immunohistochemical stains for S-100, HMB-45, and vimentin were strongly positive. The patient is free of disease 18 months after complete surgical excision.