Complexity of Breast Cancer

This is an exciting time in the study of hereditary factors involved in breast cancer susceptibility. Breast cancer for a long time was classified according histology. Now genetics play a significant role and better knowledge ensures better management and treatment.

Hereditary breast cancer (HBC) accounts for as much as 10% of the total BC burden. Only about 30 percent of these cases will be found to be due to a germline mutations in well known BRCA1 and/or BRCA2 genes, but the rest won’t have these mutations. Less than 10 percent of remaining HBC will fall into other rare conditions – and here we can see breast cancer as heterogeneous disease (ref.):

Cowden, Li-Fraumeni syndromes, heterozygosity for Ataxia telangiectasia-mutated gene (ATM) or for CHEK2 1100delC or other rare conditions Nijmegen breakage syndrome (NBS1), familial diffuse gastric cancer (CDH1), Peutz-Jeghers syndrome (STK11), Fanconi anemia (BRIP1, PALB2), Bloom syndrome (BLM)) contribute sligthly – there is consensus for ten most important genes involved in HBC (ref.)

An estimated additional 15–20% of those affected with BC will have one or more first- and ⁄ or second-degree relatives with BC (familial or polygenic breast cancer). Therefore, when these numbers are combined, familial BC risk accounts for approximately 20–25% of the total BC burden (see figure).

Here we’re talking about so called low-penetrance susceptibility genes and variants (SNPs), like rs2981582 in FGFR2, rs889312 in MAP3K1, rs3803662 in TNRC9, rs1801270 in CASP8 and many more, most of which were hot topics in the recent years. Particular alleles (particular “letter” variants of these digitalized “rs” SNPs) only increase risk slightly (twice or so) and are intense study object now, but they sooner or later will enter clinical practice.