A biplot of the original variables (relative mRNA concentrations) and tumor samples projected onto the two first principal components demonstrated that SFTPA, SFTPB and SFTPC mRNA levels were correlated with each other (arrows pointing in the same direction), whereas EPCAM and CEACAM5 and KRT19 mRNA also covariated (figure 2). The gene discussed is CEACAM5; the disease is neoplasm.