Diagnostic persistence in working up metastatic cancer with an unknown primary site.

Following initial diagnostic work-up and histological confirmation of a metastatic lesion, an extensive search may fail to locate a primary cancer site. Two case reports are presented. A retrospective analysis was done of 255 patients with metastases of unknown origin; 231 patients (over 90%) have since died. Of 34 patients with autopsy information, no primary lesion was found in 20. In the remaining 14 cases, prior knowledge of the primary site would not have influenced either therapy or proganosis. A plea is made for judicious restraint in the use of diagnostic imaging procedures to search exhaustively for a primary cancer site.