NF1 and neurofibromatosis type 1: The tumours arise from neural crest-derived cells, either sporadically or in association with the hereditary syndrome neurofibromatosis type 1 (NF1), which is caused by a germline mutation in the tumour suppressor gene NF1. The incidence of MPNST is high among patients with NF1,2 and approximately half of the cancers occur in this hereditary setting.1