Metastatic carcinoma. The lung as the site for the clinically undiagnosed primary

Of 387 patients who died with lung cancer, 28 cases were reviewed (7.2%) which were clinically undiagnosed. The male:female ratio was 3.6 and mean age was 64 years in the males, 47 years in the females. The most frequent presenting symptoms were neurologic. Prior to death, 21 patients had known or suspected metastatic disease (biopsy-proven in 12), while a malignant diagnosis was not considered in seven patients. Mean survival was 3.5 months. Despite a mean tumor size of 2.8 cm, most of the chest x-rays were not diagnostic even in retrospect. At autopsy, 65% of the tumors were adenocarcinomas (compared to 32% in the other 359 patients); 53% of these showed vascular and lymphatic invasion around the primary tumor, explaining their wide dissemination. In patients with small cell carcinomas (25% of the cases reviewed) or with solitary metastases (14% of the cases reviewed) therapeutic intervention could possibly have been beneficial.