KRT18 and neoplasm: In addition to cytomorphological analysis, gene expression of tumor associated genes (Cytokeratin-18, Cytokeratin-19, Cytokeratin-20, Cytokeratin-7, EPCAM, MUC1, HER2, EGFR) and of leukocyte markers (e.g. CD45, CD68) was tested in enriched CTC fractions.