Elastin and collagen IV double staining: A refined method to detect blood vessel invasion in breast cancer

Blood vessel invasion (BVI) is a prognostic indicator in various cancers. Elastic stain, which highlights blood vessel walls, is commonly used to detect BVI. In the breast, however, its diagnostic usefulness is limited because it also highlights some intraductal carcinoma components, which often mimic BVI. In this study, we aimed to improve BVI detection in breast cancer and developed a double staining: Victoria blue for elastin and immunohistochemistry for collagen IV. Collagen IV fibers were retained along the basement membranes of intraductal carcinoma components, whereas they were rearranged or lost in BVI. From these observations, we defined BVI as the presence of tumor cells inside an elastic ring with a rearrangement or loss of collagen IV fibers. Using these criteria, we found BVI in 148 cases (49%) among 304 cases of primary operable invasive breast carcinoma, and the presence of BVI correlated significantly with poor prognosis. By contrast, we detected BVI in 94 cases (31%) or 14 cases (5%) by elastic van Gieson or CD31 immunostaining among the same cases, respectively, with no statistically significant association with prognosis. Thus, elastin and collagen IV double staining facilitates the detection of BVI in breast cancer and is useful to predict prognosis.