Benz et al. (2006) investigated the common ERBB2 variant, G1170C, in ERBB2-positive and ERBB2-negative breast cancer patients and found that ERBB2-positive germline heterozygotes had markedly skewed tumour genotype frequencies to homozygosity of either allele and monoallelic transcript amplification25. The gene discussed is ERBB2; the disease is breast cancer.