Zinc distribution within breast cancer tissue: A possible marker for histological grading?

Focusing on the trace metal zinc as a potential biomarker for breast cancer, the literature describes bulk zinc concentrations in breast cancer tissue to be higher than in normal tissue. From a histopathological point of view, cancer cells are intermingled with normal cells of the stroma within breast cancer tissues; therefore, bulk analysis cannot reflect this situation adequately. To address this problem, analysis of zinc distribution in histological sections is the method of choice. In the present study, nine samples of invasive ductal and lobular breast carcinoma of histological grade 1-3 were investigated, clearly differentiating between cancer and stroma areas. Zinc concentrations were determined by laser ablation inductively coupled plasma mass spectrometry applying a calibration technique based on spiked polyacrylamide gels. Direct comparison between hematoxylin- and eosin-stained tissues and zinc contour plots revealed that zinc is enriched in cancer tissue containing tumor cells in contrast to normal stroma. Moreover, zinc concentration in carcinomatous tissues directly correlates with the histological malignancy grade. Differentiation between carcinomatous tissue and stroma by determination of zinc content and the correlation of zinc concentration with the histological malignancy grade not only provides a key feature for clinical decision making for cancer therapy but also suggests the trace metal zinc as a potential biomarker for breast cancer.