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Adenocarcinoma of unknown primary site

John D Hainsworth, MD
F Anthony Greco, MD
Section Editor
George P Canellos, MD
Deputy Editor
Sadhna R Vora, MD


Cancer of unknown primary (CUP) is defined as a metastatic tumor whose primary site cannot be identified during pretreatment evaluation [1]. Within this category, tumors from many primary sites with varying biology are represented. Improved radiologic and pathologic methods including gene expression profiling, immunohistochemical (IHC) staining, and positron emission tomography (PET) have improved diagnosis and allowed prediction of the site of tumor origin in most patients with CUP. However, the anatomic primary site usually cannot be detected, so that CUP patients remain a clinically distinct group. (See "Overview of the classification and management of cancers of unknown primary site".)

Adenocarcinomas of unknown primary site comprise approximately 70 percent of CUPs. In autopsy series, although tumors may arise from a wide variety of primary sites, the most frequently identified sites are lung, pancreas, hepatobiliary tree, and kidney, together accounting for approximately two-thirds of cases [2]. Adenocarcinomas of the breast and prostate are identified infrequently at autopsy, despite being the most common cancers in women and men, respectively. In 20 to 30 percent of patients, no primary site can be identified. Large autopsy series include patients who were not evaluated with modern imaging such as computerized tomography (CT) and positron emission tomography (PET), and therefore published data may not accurately reflect the current patient population with adenocarcinoma of unknown primary.

In patients with adenocarcinomas of unknown primary site, the focus is on identifying specific subsets in which disease-oriented therapy may be more effective than empiric therapy; this is based upon a combination of clinical features, IHC, and gene expression profiling.

The diagnosis and management of patients with adenocarcinoma of unknown primary are reviewed here.

The diagnosis and management of the other CUPs are discussed separately.

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Literature review current through: Nov 2017. | This topic last updated: Apr 20, 2017.
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