Pediatric malignant peripheral nerve sheath tumour of the radial nerve.

Malignant peripheral nerve sheath tumours (MPNST) are a group of malignant tumours that arise from cells that are differentiating or have differentiated toward those of the peripheral nerve sheath.1 The heterogeneity of these cellular components and stages of differentiation have historically lead to difficulty in defining the diagnosis and behaviour of these lesions, with terms such as malignant schwannoma, neurofibrosarcoma, and neurogenic sarcoma variably used to define the histopathology. Indeed, most MPNSTs do exhibit some degree of Schwannian differentiation, however this histological feature may be absent and alternately fibroblastic or perineurial cellular phenotype may predominate, with further metaplastic tissue characterizing 15% of lesions.2 These lesions usually arise de novo with rare reports of malignant degeneration from known or suspected benign disease, with known association of these lesions with Type I neurofibromatosis (NF1).3,4 The necessity of correct histological differentiation from benign tumours is based on the need for complete resection with negative tumour margins portending favourable survival prognosis, and the additional reported benefit of adjuvant therapies such as intraoperative electron radiotherapy, brachytherapy, and postoperative irradiation.5,6 Further, Anghileri and coworkers7 reviewed the literature about such lesions finding high likelihood of local recurrence (27 to 49% at five years) and substantial but variable cause specific mortality (23 to 81% at five years), reflecting heterogeneous clinical behaviour that will require further investigation to best delineate patients expected to have favourable therapeutic result. We report the case of a seven-year-old patient with biopsy demonstrated MPNST of the radial nerve who underwent complete local excision and no adjuvant therapy. This patient exhibits long-term survival, followed without secondary intervention for the last 22 years, with no evidence of local or metastatic disease recurrence. The histopathological features of pediatric MPNST will be reviewed from both the literature and this patient to assess features that may have suggested this prognosis from the index evaluation.