Breast cancer molecular subtypes--modern therapeutic concepts for targeted therapy of a heterogeneous entity.

Within the last decade, breast cancer is increasingly understood as a heterogeneous disease comprising distinct entities that vary significantly with regard to molecular biology and clinical features. Despite impressive advances in the treatment of patients with breast cancer, not all patients derive equal benefits from current therapeutic options and a significant number of patients still experience disease recurrence. Whereas for patients with hormone receptor positive and/or HER2/neu-positive breast cancer overcoming resistance against endocrine and/or anti-HER2/neu-targeted therapy is of particular importance, patients with triple negative breast cancer suffer from a lack of sufficient targeted therapeutic options at all. In this review we give a summary of the most important targeted agents recently or currently being developed for patients with breast cancer.