NERVE SHEATH TUMORS WITH HYBRID FEATURES OF NEUROFIBROMA AND SCHWANNOMA - A CONCEPTUAL CHALLENGE

Aims: To characterize and delineate a subset of rare nerve sheath tumo urs showing hybrid features of neurofibroma and schwannoma. Methods an d results: Nine lesions were identified in the authors' files showing predominant features of neurofibroma with distinct, often nodular regi ons of classical schwannomatous differentiation. Mast patients were ad ults, eight out of nine were male. Of the nine lesions, two were derma l, two were subcutaneous and five were subfascial, Five lesions had a plexiform architecture and one patient had overt neurofibromatosis, On e out of six patients with follow-up developed local recurrence. Schwa nnoma-like regions displayed strong S100 staining, in contrast to more varied and limited S100 reactivity in neurofibromatous areas. The Ant oni A areas could be quite cellular with high MIB-1 proliferation indi ces. No lesion underwent malignant change. Conclusions: Our results de monstrate that some nerve sheath tumours may contain histologically cl ear components of both neurofibroma and schwannoma, suggesting that (d espite evident and well-defined clinicopathological differences) these two lesions may be even more closely related than previously recogniz ed. Whether this phenomenon results from a localized microenvironmenta l change or from a clonal genetic alteration remains unknown.