Objective analysis of cancer stem cell marker expression using immunohistochemistry.

Analysis of immunohistochemical expression is often a subjective and semiquantitative process that can lead to the inconsistent reporting of results. To assess the effect that region selection and quantification method have on results, five different cancer stem cell markers were used in this study to compare tissue scoring with digital analysis methods that used three different tissue annotation methods. Samples of tumour and normal mucosa were used from 10 consecutive stage II colon cancer patients and stained for the putative cancer stem cell markers ALDH1, CD44v6, CD133, Lgr5 and SOX2. Tissue scoring was found to have considerably different results to digital analysis with the three different digital methods harbouring concordant results overall. However, SOX2 on normal tissue and CD133 on tumour and normal tissue produced discordant results which could be attributed to the different regions of tissue that were analysed. It is important that quantification method and selection of analysis areas are considered as part of study design to ensure that reproducible and consistent results are reported in the literature.