Molecular tumor profiling (MTP) in cancer of unknown primary site (CUP): A complement to standard pathologic diagnosis.

10560 Background: MTP may predict the tissue of origin in CUP and thus improve therapy for some patients. The ability of MTP to improve diagnosis over standard pathology is undefined. We evaluated MTP on biopsies to assess accuracy and diagnostic ability. Methods: From March 2008–January 2010 clinicopathologic data from 171 CUP patients who had MTP performed (bioTheranostics) on paraffin embedded biopsies were collected. The MTP diagnoses were validated by correlation with: 1) latent primaries found months later; 2) initial diagnosis by immunohistochemistry (IHC); 3) additional IHC and/or clinical findings after MTP; 4) clinical features, and 5) outcome of colorectal MTP patients treated with site-specific chemotherapy. Results: MTP provided a diagnosis in 144 of 171 tumors (84%); 22 had insufficient tumor for MTP (13%) and 5 were unclassifiable (3%). Histopathologic diagnoses were adenocarcinoma 56%, poorly differentiated carcinoma 27%, and others 17%. MTP diagnosed 21 tumor types [colorectal (16%), lung...