[Cancer of unknown primary site]

Patients with cancer of unknown primary site represent 0.5 to 9 percent of all cancer patients with a major incidence in people aged 50 to 70 years. The most common histological diagnosis is adenocarcinoma. The vast majority of patients have at least two different metastatic sites involved at the moment of the diagnosis. Among the identified occult primaries lung and pancreas constitute the majority. Histological diagnosis, age, sex, performance status, tumor burden and organs involved are the most important prognostic factors.

Complete medical history and physical examination are able to reveal symptoms and signs in more than 90 percent of patients. Routine laboratory tests, serum tumor markers, imaging studies and endoscopies will complete the diagnostic approach. The pathologic assessment of biopsied material is usually initiated by light microscopic examination: additional pathologic studies, including histochemistry, electron microscopy and genetic analysis are frequently and productively employed.

Locoregional treatment can be curative in a few and selected cases and is more often offered with a palliative intent. The elective treatment for metastatic disease is represented, in the vast majority of cases, by systemic chemotherapy with different schedules according to pathological diagnosis. Best supportive care is sometimes the best choice.

It is recommended to treat such patients in the context of clinical trials.