Approximately 45% present in the context of neurofibromatosis type‐1 (NF‐1), a germline tumour predisposition syndrome (incidence ~1/3,500) caused by constitutional mutations in the tumour suppressor gene neurofibromin 1 (NF1); 45% of cases occur as sporadic tumours and 10% are radiation‐associated. The gene discussed is NF1; the disease is neoplasm.