Because known oncogenes and tumor suppressor genes are also exposed to bystander mutations, only known hotspot mutations can be taken as evidence for potential oncogenic effects and protein truncating mutations as evidence for tumor suppressor function in the case of biallelic mutation (except for breast cancer associated 1 and 2 (BRCA1, BRACA2) for which gene dosage effects have been shown [26]). This evidence concerns the gene BRCA1 and neoplasm.