Representative, confocal images of a cytospin of an enriched peripheral blood sample from a SCCHN patient.

<p>This is the same patient sample used to create the cytospin presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042048#pone-0042048-g004" target="_blank">Figure 4</a>. However, for this specific, four color staining, the anti-EGFR antibody was replaced with anti-CD44. The cells highlighted with a red arrow are positive for all four markers, while cells highlighted with yellow arrows are either negative, or very weak for CK, vimentin, and CD44.