The breast cancer immunophenotype of TP53-p.R337H carriers is different from that observed among other pathogenic TP53 mutation carriers

Germline TP53 mutations are associated with Li-Fraumeni syndrome, an autosomal dominant disorder characterized by a predisposition to multiple early-onset cancers including breast cancer (BC), the most prevalent tumor among women. The majority of germline TP53 mutations are clustered within the DNA-binding domain of the gene, disrupting the structure and function of the protein. A specific germline mutation in the tetramerization domain of p53, p.R337H, was reported at a high frequency in Southern and Southeastern Brazil. This mutation appears to result in a more subtle defect in the protein, which becomes functionally deficient only under particular conditions. Recent studies show that the BC phenotype in TP53 mutation carriers is often HER2 positive (63-83 %). Considering that the immunophenotype of BC among p.R337H carriers has not been reported, we reviewed immunohistochemistry data of 66 p.R337H carriers in comparison with 12 patients with other non-functional TP53 germline mutation. Although 75 % of carriers of these mutations showed significant HER2 overexpression (3+), corroborating previous studies, only 22.7 % of p.R337H patients had BC overexpressing HER2. These results reinforce the notion that different germline mutations in TP53 may predispose to BC via different mechanisms.