[An analysis of autopsy cases with cancer of unknown primary site]

A retrospective review of autopsy cases with cancer of clinically unknown primary site seen at Shikoku Cancer Center Hospital from 1959 to 1992 was performed. Fifty three cases (3.1%) were registered as having cancer of unknown primary site among 1690 consecutive autopsy cases with malignancies except for leukemias and brain tumors. Major discrepancies on the primary site between the clinical diagnoses and the autopsy reports were present in 30 cases (1.8%). Twelve cases (0.7%) with malignancy of peritoneum or retroperitoneum primary were found that were clinically regarded as peritonitis carcinomatosa. Latent cancer, in which a new primary cancer was subsequently identified at autopsy, was recognized in 190 cases (11.2%). The mean age in latent cancer group was significantly higher than in control group, but patients with cancer of unknown primary site tended to be somewhat younger. A high male: female ratio was found in latent cancer group, whereas it was reverse in cases with clinically undetermined primary cancer. Survival overall was poor, with a median survival of 5 months. As diagnostic techniques (such as sonography, computerized tomography scanning and nuclear scans) have been improved, cases with cancer of unknown primary site have tended to decrease, but the percentage of cases presenting latent cancer has remained relatively stable over the years. Precise autopsy examination revealed that the primary sites of clinically undetermined cancers were ovary, pancreas, stomach, gallbladder and peritoneum in order of decreasing frequency. The metastatic pattern and histologic types were not different from that in the control group.