Cancer of unknown primary site

Abstract

In the United States, unknown primary cancers represented about 2% of all cancer diagnoses reported between 1973 and 1987.1 Registries from seven other countries have listed incidences from 2.3% to 7.8%.2 These patients are heterogeneous with several clinical presentations and histologic tumor types. Most have metastatic carcinoma of unknown primary site, while others have equivocal pathologic diagnoses with tumors difficult to classify by light microscopic examination. Specialized pathologic studies are essential in diagnosing the type of neoplasm present in many of these patients. © 2006 Springer Science+Business Media, Inc.