The complex genetic landscape of familial breast cancer.

Familial breast cancer represents a minor percentage of all human breast cancers. Mutations in two high susceptibility genes BRCA1 and BRCA2 explain around 25 % of familial breast cancers, while other high, moderate and low susceptibility genes explain up to 20 % more of breast cancer families. Thus, it is important to decipher the genetic architecture of families that show no mutations to improve genetic counselling. The comprehensive description of familial breast cancer using different techniques and platforms has shown to be very valuable for better patient diagnosis, tumour surveillance, and ultimately patient treatment. This review focuses on the complex landscape of pathological, protein, genetic and genomic features associated with BRCA1-, BRCA2-, and non-BRCA1/BRCA2-related cancers described up to date. Special emphasis deserves the coexistence of distinct molecular breast cancer subtypes, the development of tumour classifiers to predict BRCA1/2 mutations, and the last insights from recent whole genome sequencing studies and miRNA profiling.