The prognostic relevance of HER2-positivity gain in metastatic breast cancer in the ChangeHER trial

Breast cancer (BC) heterogeneity is composite in nature, with a wide variety of factors concurring to define several pathological entities, which differ by clinical presentation, pathologic features, therapy administered, and inherent outcomes1. Additional sources of breast cancer heterogeneity may raise during the disease course. In BC patients whose disease was initially diagnosed in the early stage and subsequently progressed with metastatic involvement of one single or multiple site/s, the molecular characteristics of metastatic lesions do not necessary mimic those of the disease initially diagnosed. A well-depicted molecular landscape is crucial for subtype definition, prognostic evalu…