 Pathologists routinely attempt to decipher the site of origin using extensive immunohistochemical staining, however, the rate of identification remains low. Modern cancer therapeutics including immune checkpoint inhibitor therapies are specific to the primary tumor hence broad-spectrum chemotherapy remains the standard-of-care for CUP patients\mbox{%DIFAUXCMD massard2011carcinomas .
<clarity>  Pathologists routinely attempt to decipher the site of origin using extensive immunohistochemical staining, however, the rate of identification remains low. Modern cancer therapeutics including immune checkpoint inhibitor therapies are specific to the primary tumor hence broad-spectrum chemotherapy remains the standard-of-care for CUP patients\mbox{%DIFAUXCMD massard2011carcinomas .
 This poses a significant challenge since modern therapeutics such as chemotherapy regimen and immune checkpoint inhibitors are specific to the primary tumor hence broad-spectrum chemotherapy remains the standard-of-care for CUP patients\mbox{%DIFAUXCMD massard2011carcinomas .