The histology of the engrafted tumor retains morphologic features of the primary patient tumor as assessed by a Board Certified Pathologist. IHC for human Ki67 validates that the tumor cells are actively dividing and are of human origin. IHC for CD45 and cytokeratin (AE1/AE3) rules out a xenograft-associated lymphocytic tumor. STR analysis validates provenance of engrafted tumor.