[Metastasis of an unknown primary tumor, management attuned to histopathology]

Metastases from an unknown primary tumour are found as the first expression of a disease process in about 5-10% of all cancer patients. This situation triggers two subsequent questions: what kind of tumour is it and where does it come from? In the management of these patients close cooperation between the clinician and pathologist is essential. Overdiagnosis and overtreatment should be avoided in these patients, 85% of whom will not survive one year. By combining morphological examination of cell or tissue preparations with immunohistochemistry the pathologist is able to provide reliable information on the type and sometimes the origin of the tumour, as a result of which those malignancies worth treating can be identified. Applying pathological investigation at an early stage may reduce the need for diagnostic imaging and endoscopic investigations.