A novel HER2-positive breast cancer phenotype arising from germline TP53 mutations
The Li-Fraumeni Syndrome is caused by a germline TP53 mutation and is associated with a high risk of breast cancer at young ages. Basal (triple negative) breast cancers are now well recognised to be a typical sub-type of breast cancer developing in a large proportion of BRCA1 gene carriers. We considered whether a similar narrow sub-type of breast cancer was found in TP53 gene mutation carriers. A hypothesis generating study to investigate whether there are specific breast tumour characteristics associated with germline TP53 mutations. Pathological characteristics in 12 breast cancers arising in nine patients carrying pathogenic TP53 mutations were compared to a reference panel of 231 young onset breast tumours included in the POSH study. Patients carrying a TP53 mutation showed a significantly higher likelihood of developing a breast cancer with Human Epidermal growth factor Receptor (HER2) amplification (83%) when compared to the cohort of young onset breast cancer cases (16%); ER and PR status were equivalent between groups. These findings suggest that breast cancer developing on a background of an inherited TP53 mutation is highly likely to present with amplification of HER2.