摘要：Breast cancer (BC) is the most common cancer among women, with nearly 1.7 million new cases diagnosed in 2012 worldwide, ranking as the fifth cause of death for cancer (522,000 deaths/y). The wide introduction of molecular analyses allowed the comprehension that BC is not a single entity but should be divided into, at least, 4 major subtypes: Luminal A, Luminal B, HER2 positive and triple negative/basal-like. Luminal Breast Cancer (LBC) represents the most common subtype, accounting for more than 60% of all diagnosed BC. In clinical practice, only few characteristics, such as Estrogen Receptor (ER), Progesteron Receptor (PR), HER2 and Ki67 expression, are currently used to distinguish Luminal A (LBC-A) (ER+ and/or PR+, HER2-, low Ki67) and Luminal B (LBC-B) (ER+ and/or PR+ HER2- or HER2+, high Ki67) [1]. However, this oversimplified classification has profound therapeutic implication, since based on the relative expression of these markers, LBC patients will or will not receive hormone-, chemo- or targeted- therapies [1]. When compared with LBC-A, LBC-B displays higher rate of early recurrences and worse prognosis and represents a subgroup for which the choice of the optimal therapy still represents a difficult task for the clinician [1]. In fact, clear biomarkers to select the most appropriate (hormone- with or w/out chemo-) therapy in LBC-B, still have to be validated and introduced to the clinic [1].
