title: Synchronous and metachronous diagnosis of multiple primary cancers.
abstract: OBJECTIVE
  In the time period near to the diagnosis of a new cancer, other tumors (synchronous cancers), especially slow-growing tumors, may be detected because several diagnostic examinations are performed. The frequency of synchronous in comparison with metachronous carcinomas has been evaluated in a population-based series of multiple primary cancers.
  
  
  METHODS
  The case series of multiple primary cancers of the Tuscany Tumor Registry, incident during the period 1985-1991 was analyzed. For each site of a second independent tumor, the proportions of synchronous (diagnosed within 2 months of the first primary) and metachronous cancers were compared with the mean distribution (all sites except the specific one).
  
  
  RESULTS
  During 1985-1991, 1095 patients had two independent tumors diagnosed; 216 were synchronous. The proportion of synchronous compared to metachronous cancers was significantly higher for bladder, prostate and renal cell carcinomas; it was significantly lower for lung cancer. When cancers following skin epitheliomas were evaluated, only the proportion of synchronous skin cancers was significantly increased.
  
  
  CONCLUSIONS
  Silent slow-growing tumors are suspected to be more frequent in patients with prostate, bladder or renal cell carcinomas. In fact, they were most frequently diagnosed during ascertainment for another cancer. When few examinations were performed, as after the diagnosis of a skin epithelioma, no difference between metachronous and synchronous cancers was evident, except for skin.
authors.affiliation: Registro Tumori Toscano, Firenze, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Crocetti
authors.forename: S
authors.initials: S
authors.lastname: Arniani
authors.forename: E
authors.initials: E
authors.lastname: Buiatti
mesh_terms: D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D009378:Neoplasms, Multiple Primary / Q000175:diagnosis* / Q000453:epidemiology; D012042:Registries; D013997:Time Factors