TO THE EDITOR: Chiang et al are correct that gene expression profilinginpatientswithcancerofunknownprimary(CUP)canbeuseful and in some instances complements immunohistochemistry in determining the primary cancer site or tissue of origin in these patients. However, thecasepresentedisprobablynotCUP,but illustrateswelloneof the limitations of gene expression profiling in patients with suspected CU...