Identification en pratique clinique des carcinomes basal-like du sein : des carcinomes « triple zéro/BRCA1-like »

Basal-like carcinomas represent 10 to 15% of invasive breast carcinomas and have been identified from gene expression studies. Morphologically, these tumors are undifferentiated histopronostic grade 3 carcinomas, identified in clinical practice according to their immunophenotype “triple zero” (estrogen, progesterone and ERBB2 negative) associated with the high molecular weight cytokeratins 5/6/14 and/or EGFR expression. At the molecular level, these tumors harbour nearly 100% P53 mutations, a high rate of PTEN mutations with an AKT pathway's activation and numerous chromosomal alterations such as gains and losses. They share a high degree of similarity at the morphological, phenotypical and molecular level with BRCA1 tumors that justify the proposal of a different name such as “triple zero/BRCA1 like” carcinomas for sporadic basal-like carcinomas. Indeed, the current “basal-like” name could suggest a myoepithelial cellular origin of such lesions. Furthermore, tumors with such a basal-like immunophenotype constitute a heterogeneous group of tumors encompassing good prognosis tumors such as adenoid cystic and juvenile secretory carcinomas. There is an urgent need for more specific therapies for basal-like/triple zero/BRCA1-like tumors. Therapeutic progresses rely on a better understanding of the molecular alterations that occur in these tumors and the BRCA1 tumors. Indeed, recent clinical trials with PARP inhibitors for basal-like/BRCA1 like tumors should improve the prognosis of these patients and are a direct benefit of a better understanding of the molecular biology of these tumors.