Vascular proliferation is increased in basal-like breast cancer.

Based on molecular sub-classification, basal-like breast cancer is associated with aggressive behavior. These tumors are frequently triple negative and lack traditional treatment targets. Angiogenesis, one of the hallmarks of cancer, is important for the local growth and spread of malignant tumors and is now a treatment target. The aim of this study was to explore whether angiogenesis is increased in relation to certain molecular subtypes of breast cancer with special focus on the basal-like category. Altogether, we analyzed a total of 431 breast cancers from two independent series after dual immunohistochemical staining of Factor VIII for endothelial cells and Ki-67 for proliferating cells. We then determined vascular proliferation in the most vascularized areas of the tumor. In both Series I and II, high vascular proliferation index (VPI) was significantly associated with expression of cytokeratin 5/6 (P = 0.001, 0.010), P-cadherin (P < 0.0005, <0.0005), epidermal growth factor receptor (P = 0.003, 0.001), the basal-like subtype (P = 0.001, 0.011), and the core basal phenotype (P = 0.002, 0.002), respectively. In Series I, high VPI was associated with the triple negative phenotype (P = 0.004) and p63 expression (P = 0.008). Tumor angiogenesis, as measured by vascular proliferation, was increased in the basal-like subtype in two independent breast cancer series and may thus be a possible treatment target in this category. Studies are required to evaluate whether this novel angiogenesis marker can be used to stratify patients for anti-angiogenesis treatment.