Primary Site Unknown

Abstract

Cancer of unknown primary site is a neoplastic bastard, a child without a father. When metastases rather than the primary tumor cause signs or symptoms the diagnosis of cancer is often made from the metastases. More often than not, the search for the primary tumor is successful. Liver metastases usually come from the gastrointestinal tract but may come from very small breast or lung primary tumors. Metastases in neck lymph nodes should be the consequence of an occult primary tumor in the head and neck, but sometimes even primary tumors below the diaphragm metastasize to neck nodes. When the search for the primary source of metastases is unsuccessful, the appellation “primary site unknown” is appropriate. In published series these comprise 0.5%–5% of cancers (Didolkar et al. 1977; Holmes and Fouts 1970).