Little is known on functional consequences of NF1 mutation allelic balance in cancer cells.33, 34, 35 It has become apparent that not all consistent loss‐of‐function hits in tumor suppressor genes are accompanied by obvious aberrations on the WT allele, in discordance with the two‐hit hypothesis affecting tumor suppressor genes.36 Single‐copy loss may have a role in tumorigenesis, and haploinsufficiency effect may be highly tissue specific and context dependent. The gene discussed is NF1; the disease is cancer.