To minimize the confounding influence of patients with somatic mosaicism for NF2 gene mutations among patients with suspected schwannomatosis, Piotrowski et al. (2014) included in their analysis of SMARCB1 mutation-negative patients only those individuals who exhibited different somatic NF2 gene mutations and LOH of chromosome 22q in at least two different tumours analysed. The gene discussed is SMARCB1; the disease is neoplasm.