Relationships between vascularization and proliferation in invasive breast cancer

Studies on relationships between angiogenesis and tumour cell proliferation have provided conflicting results. This study has therefore investigated the relationships between the number and location of fully automatically identified CD31-positive microvessels and interactively segmented mitoses and necrotic compartments by image processing. These features were studied in ten invasive breast cancers, in the 'hot spots' and in whole tumour sections. Microvessel and mitosis hot spots were topographically close or overlapping and were always located at the periphery of the tumour. The numbers of mitoses and microvessels per mm² in the hot spot were strongly correlated with the respective numbers in the whole tumour section, as well as mutually. The ratio of mitoses in the hot spot to the whole tumour section was significantly higher than the corresponding microvessel ratio. Mitoses were preferentially located at a distance of 50- 150 μm from microvessels. No significant difference was found between the average distance between mitoses and microvessels in the whole tumour sections and in the hot spot (79 vs. 72 μm), although considerable inter- tumour differences were found (hot spot 43-101 μm, tumour 47-111 μm). The presence of necrotic areas correlated with the number of mitoses per mm² and necrosis was in general observed at a distance of more than 150 μm from the microvessels, suggesting that necrotic areas have outgrown their vascular system. These results indicate the usefulness of image processing of whole tumour sections for the identification of proliferation and vascularization hot spots, which are strong prognostic factors in breast cancer. The results also support a close relationship between tumour necrosis and microvessels.