Malignant peripheral nerve sheath tumor of bone in children and adolescents

Malignant peripheral nerve sheath tumor (MPNST) of bone is a rare entity. W e have examined three lesions that fit standard histopathologic criteria fo r MPNST of soft tissues but that arose in the skeleton of three children ag ed 6 to 13 years. None was affected by neurofibromatosis 1 (NF1). Histologi c features typical of MPNST included spindle cells with comma-shaped nuclei , tactoid bodies, nuclearpalisading, hyaline bands, and schwannoma-like and curlicue foci. Epithelioid foci were seen in two cases, and heterologous d ifferentiation in one. Immunohistochemistry revealed positivity for S-100 ( 1 positive/3 tested), vimentin (3/3), glial fibrillary acidic protein (2/3) , CD34 (1/1), and CD68 (1/2). Studies for CD99 (0/3), epithelial membrane a ntigen (0/3), cytokeratin (0/3), CD57 (0/3), and HMB-45 (0/2) were negative . Ultrastructural findings in one of two cases examined included interlacin g, attenuated cytoplasmic processes, microtubules, and rare dense-core gran ules. We conclude that MPNST may arise as a primary bone neoplasm in childr en without NF1.