To compare the S100A6 staining pattern with that of cytokeratin 5 and cytokeratin 18, tissues arranged in a TMA, comprising of 19 cases of matched adenocarcinoma, benign epithelium and benign stroma were serially cut and immunostained for cytokeratin 5 (a marker of prostate basal cells), or cytokeratin 18 (a marker for benign luminal cells), which is also expressed in malignant cells (Freeman et al, 2002). The gene discussed is KRT5; the disease is adenocarcinoma.