Metastatic cancer of unknown primary site

Characteristics of 686 patients with the diagnosis of metastatic cancer of unknown primary site are examined. Average age of the series is 60.2 years and ratio of males to females is 58:42. Bones, lungs, and liver are the common sites of metastases, and adenocarcinoma, carcinoma, and anaplastic carcinoma are the most common histologic types. Survival for all patients is: 2‐year 10.4%, 5‐year 5.1%, and 10‐year 3.3%. Average age of the 27 patients surviving 5 years or longer is 52.5 years of the 14 patients of this latter group now dead, only 2 died of cancer. Speculation about both elusive primary tumors and occasional long survival must include primary tumors too small to be found at either clinical examination or autopsy, inadvertent removal or destruction of primary earlier by physician or sloughing by host, or destruction or containment of tumor by host defense mechanisms.