Nerve sheath tumours with hybrid features of neurofibroma and schwannoma: a conceptual challenge

TLDR

The origin of hybrid neurofibroma–schwannoma tumors—whether due to microenvironmental changes or clonal genetic alterations—remains unclear. The study seeks to characterize and delineate rare nerve sheath tumors that display hybrid neurofibroma and schwannoma features. In nine adult male lesions, most were subfascial with plexiform architecture; schwannoma‑like regions showed strong S100 staining and high MIB‑1 indices, whereas neurofibromatous areas had variable S100, and none progressed malignantly, indicating that hybrid tumors contain distinct neurofibroma and schwannoma components and may be more closely related than previously thought.

Abstract

To characterize and delineate a subset of rare nerve sheath tumours showing hybrid features of neurofibroma and schwannoma.Nine lesions were identified in the authors' files showing predominant features of neurofibroma with distinct, often nodular regions of classical schwannomatous differentiation. Most patients were adults, eight out of nine were male. Of the nine lesions, two were dermal, two were subcutaneous and five were subfascial. Five lesions had a plexiform architecture and one patient had overt neurofibromatosis. One out of six patients with follow-up developed local recurrence. Schwannoma-like regions displayed strong S100 staining, in contrast to more varied and limited S100 reactivity in neurofibromatous areas. The Antoni A areas could be quite cellular with high MIB-1 proliferation indices. No lesion underwent malignant change.Our results demonstrate that some nerve sheath tumours may contain histologically clear components of both neurofibroma and schwannoma, suggesting that (despite evident and well-defined clinicopathological differences) these two lesions may be even more closely related than previously recognized. Whether this phenomenon results from a localized microenvironmental change or from a clonal genetic alteration remains unknown.