certain dyes used 4 sentinel node (Identification) biopsy causes false ER negativity

[Lani]

or lower ER positivity than the true value. One of these dyes was methylene blue in certain concentrations--

The presence of ER in breast cancer is an established prognostic marker determining the likelihood of response to anti-hormonal therapy. PR is a marker of ER functionality. ER-positive and PR-positive tumours are more likely to respond to anti-hormonal treatment than ER-positive and PR-negative tumours; there is some evidence that ER-positive and PR-negative tumours are more likely to respond to aromatase inhibitors than tamoxifen.9–11 In this study, we have explored the hypothesis that the dyes used in SLNB could interfere with hormonal receptor determination. A significant diminution in scoring was seen with cells treated with MB at 1:10 and 1:100 dilutions, with some samples rendered negative. This was not seen with PBV and IDC (table 1). These results suggest that an inherently weak ER expresser could be rendered negative after exposure to MB with consequent withholding of potentially beneficial treatment. However, it is difficult to accurately relate in vitro findings to an in vivo situation. No similar effect was seen on the results of MNF116 immunolabelling, and the effects of these dyes on other markers would need case-by-case evaluation.