Quantifying tumour vascularity in non-luminal breast cancers

Microvessel density (MVD), proliferating MVD (pMVD) and vascular proliferation index (VPI) are methods used to quantify tumour vascularity in histopathological sections. In this study, we assessed MVD, pMVD and VPI in non-luminal subtypes of breast cancer. Differences between subtypes were studied, and the prognostic value of each method was assessed.

All non-luminal subtypes (61 basal phenotype (BP), 60 human epidermal growth factor receptor 2 (HER2) type and 30 five negative phenotype (5NP)) were selected from a series comprising 909 cases of breast cancer. Sections were stained for Ki67 and von Willebrand factor. Associations between MVD, pMVD and VPI, molecular subtypes and prognosis were studied.

MVD was highest in 5NP (54.3 microvessels/mm² compared with BP, 95% CI 30.3 to 78.3), whereas no clear difference was found between HER2 type and BP (8.8 microvessels/mm², 95% CI –9.6 to 27.1). pMVD and VPI did not differ between subtypes. For MVD, HR was 1.07 (95% CI 1.03 to 1.11) per 10 vessel increase and 1.9 (95% CI 1.2 to 3.1) if MVD was greater than median value. High MVD was associated with poor prognosis in the HER2 type (HR 1.07 (95% CI 1.02 to 1.12)) and 5NP (HR 1.13 (95% CI 1.03 to 1.23)), but not in BP (HR 1.04 (95% CI 0.94 to 1.14) per 10 vessel increase). pMVD and VPI were not associated with prognosis.

MVD appears to be an independent prognostic factor in HER2 and 5NP subtypes of breast cancer, where high MVD is associated with poor survival. MVD was higher in the 5NP compared with both BP and HER2 type.