As a group, TNBCs have been shown to be characterized by high levels of genetic instability, with a median of 1.7 (range 0.16–5.23) mutations/Mb,14,15 and complex patterns of copy number alterations (CNAs) and structural rearrangements.16 Unlike other forms of breast cancer, where several genes have been found to be mutated in >10% of cases, the only known cancer genes targeted by somatic mutations in 10% or more of TNBCs are TP53 and PIK3CA (Figure 2). This evidence concerns the gene PIK3CA and cancer.