Influence of investigator experience and microscopic field size on microvessel density in node-negative breast carcinoma

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Abstract
In this study on the determination of intratumoralmicrovessel density (MVD) in breast cancer, we haveinvestigated the influence of the observer experience andthe microscopic field size. We have used thesample set reported on earlier in the JNatl Cancer Inst 87: 1797–1798, 1995. This case-controlstudy has shown a positive association of highMVD and unfavorable outcome when comparing node-negative pT1–2breast carcinoma (NNBC) patients with a disease-free periodof over ten years with those with anearly distant relapse.Tumor sections of both outcome groups (favorable: n= 19; unfavorable: n = 19) were immunostainedfor factor VIII related-antigen (FVIII r-Ag). Microvessels werecounted in the areas of most intense vascularization(‘hot spots’), both at magnification × 200 (fieldsize of 0.61 square mm) and × 400(field size of 0.15 square mm), by oneinexperienced and three experienced observers. Microphotographs of individualvascular hot spots were analyzed using overlays resemblingthe two field sizes.The main results obtained are: i) a confirmationof the prognostic value of microvessel density inthe case-control sample set (n = 38) wasestablished by all experienced but not by theunexperienced investigator; ii) both at × 200 and× 400 magnification, angiogenesis quantification in vascular hotspots contained prognostic information.The results of this study indicate that theselection of vascular hot spots in tumor sectionsimmunostained for an antigen expressed on endothelial cellsis more prone to inter-observer variability and moredependent on training than the counting of themicrovessels within predefined hot spots itself. The microscopicmagnification and resulting field size do not influencethe prognostic significance of MVD in NNBC. Thisinformation validates the development of more objective methodsof measuring the amount of angiogenesis within malignanttissue. This will allow more accurate implementation ofthe angiogenesis parameter in multiparametric and prospective prognosticfactor studies in NNBC.