Primary Versus Metastatic Cancer: Gene Expression Profiling

Abstract

Accurate identification of the primary site of a cancer is important to predict prognosis and select appropriate therapy. Approximately 10%–15% of cancers initially present as metastases to solid organs, body cavities, or lymph nodes. However, the primary site of the metastatic cancer is not always clinically apparent. About 3%–5% of all cancers are carcinomas of unknown primary, making this type of tumor one of the 10 most frequent cancers in the world.1, 2, 3, 4, 5, 6, 7, 8, 9 Even with autopsy, in a series published in 2005 by Al-Brahim et al., a primary site was identified in only 51% of 53 cases of metastatic cancer of unknown origin.9