Carcinoma of unknown primary with a colon-cancer profile-changing paradigm and emerging definitions.

Carcinoma of unknown primary (CUP), which accounts for about 3-5% of all new cancers, is a challenging heterogeneous entity with an unmet research need. Traditionally, CUP has been managed with broad-spectrum chemotherapy, but with the increasing availability of sophisticated diagnostic techniques and the emergence of new treatments that have been shown to be effective in specific cancers the one-treatment-fits-all approach to CUP might eventually no longer be valid. CUP in association with a colon-cancer profile (CCP-CUP) is an example of an emerging, specific CUP subset that seems to benefit from a tailored approach. CCP-CUP is identified by CK20 and CDX2-positive and CK7-negative immunohistochemistry and a clinical course consistent with that of patients known to have metastatic colon cancer. Our findings suggest that patients with CCP-CUP derive substantial benefit from the use of specific treatments developed for colon cancer and larger clinical trials are warranted to more definitely test this finding. In the era of molecular profiling, we expect that additional work with CCP-CUP and other CUP subsets will provide attractive tailored treatment alternatives, with efficacies that exceed the current one-treatment-fits-all approach.