[Cancers of unknown origin: 311 cases]

Carcinoma of unknown primary site has been defined as a metastatic disease without known primary site (upon clinical, radiological or endoscopic examination) at the initial therapeutic decision. The incidence of such carcinomas is between 1.6 and 15% of all adult's tumors. The goals of this retrospective and monocentric study were 1) the incidence of these carcinoma; 2) the utility to identify the primary site; 3) the efficacy of treatment in terms of survival; and 4) the prognostic factors to optimize strategic choices. Between January 1980 to December 1995, 311 cases were identified; this represents 1.6% of all cases treated in our center. Histological analyses of metastases revealed adenocarcinoma: 164 cases (92 males, 72 females; 29 well differentiated, 11 poorly differentiated and 41 undifferentiated); squamous cell carcinoma: 90 cases (78 males, 12 females); undifferentiated carcinoma: 27 cases (21 males, 6 females); neuro-endocrine tumor: 10 cases; and others: 20 cases. Median age was 61.1 years (30-94). Half of the patients had a PS between 0 and 1. The carcinoma was revealed by only one site of metastases in 35% of the cases (lymph node 72.9%, bone 35.5%, liver 19.4% and lung 16.5%). The primary carcinoma was found in only 6% of the cases. Median survival of all patients was only 9 months. Multivariate analyses by the Cox method show four positive prognostic factors: sex (female), performance status (PS < 2), histological analyses (squamous cell carcinoma), only one site of metastases.