Pathological changes in the PDX following treatment with erlotinib.

<p>A. The control xenograft was composed largely of compact tissue with only a minority of loose, less cellular tumor. B. Loose, discohesive, less cellular areas were more common in erlotinib-treated xenografts. C and D. Nuclei in the control (C) and erlotinib (D) treated xenografts were immunoreactive for brachyury. E. Control treated xenografts had a brisk Ki-67 index. F. Ki-67 indices were generally lower in erlotinib-treated xenografts. Magnifications: A and B, 64X; C and D, 160X; E and F, 100x.