Tumors of Unknown Primary

The term “Cancers of Unknown Primary Site” (CUP) is usually associated with metastatic lesions for which a primary site of origin has not been identified (Pavlidis et al., Eur J Cancer 39(14):1990–2005, 2003). In approximately 3% of all adult patients with carcinomas, the site of origin is not identified. Pediatric patients also present with metastatic tumors that have no identifiable primary. The distribution in children includes similar “adult type” carcinomas, but also, embryonal cancers such as rhabdomyosarcoma and neuroblastoma (Kuttesch et al., Cancer 75(1):115–121, 1995). The strategy must include diagnostic imaging studies and molecular profiling techniques that may identify the tissue of origin. It is not clear if these techniques can direct treatment that may improve outcome. In the case of pediatric tumors of unknown primary site, the introduction of more modern imaging and molecular techniques has reduced the incidence of “true” pediatric CUPs. In 2011, the pediatric oncologist seeking to identify the site of origin of these unusual tumors has more advantages with improved imaging and molecular pathology techniques. CUPs provide great challenges for the pediatric oncologist. We hope to present some common sense strategies that might prove beneficial. We caution everyone, that given no data, the clinician must be imaginative.