This study shows that the multiplex assay provides accurate determinations of CEACAM5, KLK6, SLC35D3, POSTN, and MUC2 mRNA levels in RNA extracts from tissue volumes as small as a few sections of formalin-fixed tissue, and that analysis of CEACAM5 mRNA in such extracts is a more sensitive technique than histopathology for the detection of disseminated tumor cells. This evidence concerns the gene SLC35D3 and neoplasm.