Differences among peritoneal and pleural mesothelioma: data from the Lombardy Region Mesothelioma Register (Italy).

The relationship between asbestos exposure and peritoneal mesothelioma (PEM) is under investigation. Some authors suggest that the association could be weaker than that observed for pleural mesothelioma (PLM).To compare individual, clinical and exposure characteristics of peritoneal and pleural mesothelioma cases that occurred in the Lombardy Region (Italy).Cases were drawn from the regional mesothelioma registry (base population > 9 million). We selected all PEM cases diagnosed between 2000 and 2007 (N = 110) and all PLM cases that occurred between 2000 and 2001 (N = 515). Asbestos exposure data (occupational, environmental/familial, or both) were collected by a standardized and validated questionnaire administered to each case or case's relative. Based on available chest CT scans, we also investigated the concomitant presence of asbestosis and/or pleural plaques as markers of asbestos exposure.PEM and PLM cases had similar proportions of occupational (around 60\%) and environmental/familial (7\%) asbestos exposure. The proportion of PEM subjects with co-existent occupational and environmental/familial exposures was, however, twice as high as PLM cases (6.1\% vs 3.1\%). Asbestosis and pleural plaques were more frequent in PEM than in PLM cases (7.7\% and 20.9\% vs 0.4\% and 12.1\%, respectively). No differences were detected for duration of exposure and latency among occupationally exposed cases.Our findings from a population-based Registry suggest that high cumulative asbestos exposures are the main risk factors not only for pleural but also for peritoneal mesothelioma.