Examination of 9 primary tumors and 8 matching lymph node metastases using IHC or immunofluorescence (Fig. 3A–F) (representative of poorly differentiated squamous cell carcinoma with high sarcomatoid differentiation) revealed that CD49f expression in these tumors was limited to subpopulations representing 5–18% (Fig. 3) of all tumor cells. This evidence concerns the gene ITGA6 and squamous cell carcinoma.