INFLUENCE OF INVESTIGATOR EXPERIENCE AND MICROSCOPIC FIELD SIZE ON MICROVESSEL DENSITY IN NODE-NEGATIVE BREAST-CARCINOMA

In this study on the determination of intratumoral microvessel density (MVD) in breast cancer, we have investigated the influence of the obs erver experience and the microscopic field size. We have used the samp le set reported on earlier in the J Natl Cancer Inst 87: 1797-1798, 19 95. This case-control study has shown a positive association of high M VD and unfavorable outcome when comparing node-negative pT1-2 breast c arcinoma (NNBC) patients with a disease-free period of over ten years with those with an early distant relapse. Tumor sections of both outco me groups (favorable: n = 19; unfavorable: n = 19) were immunostained for factor VIII related-antigen (FVIII r-Ag). Microvessels were counte d in the areas of most intense vascularization ('hot spots'), both at magnification x 200 (field size of 0.61 square mm) and x 400 (field si ze of 0.15 square mm), by one inexperienced and three experienced obse rvers. Microphotographs of individual vascular hot spots were analyzed using overlays resembling the two field sizes. The main results obtai ned are: i) a confirmation of the prognostic value of microvessel dens ity in the case-control sample set (n = 38) was established by all exp erienced but not by the unexperienced investigator; ii) both at x 200 and x 400 magnification, angiogenesis quantification in vascular hot s pots contained prognostic information. The results of this study indic ate that the selection of vascular hot spots in tumor sections immunos tained for an antigen expressed on endothelial cells is more prone to inter-observer variability and more dependent on training than the cou nting of the microvessels within predefined hot spots itself. The micr oscopic magnification and resulting field size do not influence the pr ognostic significance of MVD in NNBC. This information validates the d evelopment of more objective methods of measuring the amount of angiog enesis within malignant tissue. This will allow more accurate implemen tation of the angiogenesis parameter in multiparametric and prospectiv e prognostic factor studies in NNBC.