Diverse differentiation in malignant peripheral nerve sheath tumours associated with neurofibromatosis-1: an...

The diverse histological features in malignant peripheral nerve sheath tumours (MPNSTs) associated with NF-1 were investigated by immunohistochemical and electron microscopic analysis. Our study is focused on the differentiation of the tumour cells in the heterogeneous components.

Twenty-three cases were classified as conventional type, epithelioid type, anaplastic type, and heterogeneous type, and divided into three groups by the presence of S100 protein (S100)-positive cells in each tumour; Group A was defined as having >50% S100+ cells, Group B as having <50%, and Group C as cases with no positive cells. To investigate the differentiation of the tumour cells, the morphology and immunoreactivity for neural or mesenchymal markers among the three groups were compared. For the identification of Schwannian, perineurial, and endoneurial differentiation, markers for S100, EMA and CD34 were used, respectively. In three tumours of the Group A type, there were no cases showing differentiation towards perineurial or endoneurial cells, or formation of heterogeneous components. In nine tumours of the Group B type, one tumour expressed EMA and CD34, suggesting probable perineurial and/or endoneurial differentiation. One tumour showed rhabdomyoblastic differentiation. Three tumours showed cartilaginous or osteogenic differentiation, and one of the three also showed a focal vascular differentiation. The surrounding areas of the heterogeneous components were composed of mixed S100+ cells and S100- cells. S100- cells in the areas were positive for CD34 in one case. In 11 tumours of Group C type, one tumour expressed EMA and CD34 suggesting perineurial and/or endoneurial cell differentiation. Three tumours showed rhabdomyoblastic differentiation. The tumour cells around the heterogeneous components in the three cases were negative for EMA and CD34.

Our results suggest that tumour cells differentiating to Schwann cells are not the only component of MPNSTs. Furthermore, tumour cells other than Schwann cells are largely related to the formation of the heterogeneous components in MPNSTs associated with NF-1.