Managing carcinomas of unknown primary site.

Patients with carcinoma of unknown primary site are heterogeneous with respect to tumor biology, clinical characteristics, and response to therapy. These patients should no longer be considered uniformly "untreatable"; careful evaluation can identify treatable subsets. The initial light microscopic findings should be used to categorize patients into one of three groups: Well-differentiated adenocarcinoma, poorly differentiated carcinoma (or adenocarcinoma), and squamous carcinoma. Subsequent evaluation and treatment differ for these three groups. Poorly differentiated carcinomas are often responsive to cisplatin-based chemotherapy; effective systemic treatments are also available for some subsets of patients with adenocarcinoma. Surgery and/or radiotherapy is often beneficial for patients with squamous carcinoma, especially those who have isolated cervical lymphadenopathy.