Review of primary unknown cancer: cases referred to the National Cancer Center Hospital East

Primary unknown cancer (PUC) is not rare neoplasm. The clinical features and survival time of these patients are heterogeneous. We analyzed cases that were referred to the National Cancer Center Hospital East with preliminary diagnosed PUC to evaluate the natural history and clinical features. We retrospectively reviewed medical records of PUC patients who were referred to our institution between August 2005 and December 2008. One hundred and twenty-six patients with preliminary diagnoses of PUC were referred to the National Cancer Center Hospital East from community hospitals. The median age was 63 years (range 31-89 years). Almost all patients (85.7%) had good performance status (0-1). The mean interval between the first visit to a community hospital and referral to our hospital was 3.66 months (range 0-60 months). In 41 patients (32.5%), primary malignancies were identified by immunohistochemical studies and radiographical workup after referral to our hospital. Twenty-eight patients (22.2%) were defined as belonging to favorable subsets. About 50% of patients with unfavorable subsets received chemotherapy. None of the patients were autopsied. In about half of the patients with preliminary diagnosed PUC, the primary origin could be identified, or it was possible to distinguish subsets with favorable prognosis.