20513 Background: Sarcomas are rare malignant tumors reported to account for 1% of all adult tumors - respectively 1–3 per 100,000 persons per year for soft tissue sarcomas (STS) and less than 0.5 for bone sarcomas (BS). There are more than 50 histological subtypes of STS, each with its own clinical management. Within the context of an evaluation of medical practices, we decided to assess the medical management of all sarcoma patients seen in one year in the Rhone-Alpes (RA) region which represents 10% of the total French population. One of the secondary objectives was to assess the incidence of sarcomas. About 1,800 STS cases are diagnosed each year in France, hence 200 new sarcomas (STS, BS, visceral) were expected in the region. Methods: A prospective and exhaustive collection of pathology data was launched in direct collaboration with the network of pathologists in the RA region. All patients in primary care, above 15 years old, and diagnosed with sarcoma from March 2005 to Feb 2006 in RA were included. Collection comprehensiveness was checked. Results: In one year, 417 patients met inclusion criteria and were analyzed: 65% STS (n=270), 20% visceral sarcomas (Gastro Intestinal Stromal Tumor (GIST), uterine sarcomas) (n=84), 12% BS (n=49) and 3% undifferentiated malignant tumors (n=14). The most frequent histological subtypes were GIST (17% n=72), liposarcomas (17% n=71), leiomyosarcomas (9% n=38). 27% og sarcomas were not otherwise specified (NOS) (n=74). 5 patients were between 15 and 18 years old at diagnosis. Conclusions: The first year of inclusion showed an incidence of sarcomas twice higher than reported in the literature. French registris classify tumours per organ site, leading to an underestimation of the number of cases. This is partly due to the non-identification of GIST or uterine sarcomas. This study raises the question of a need for a national registry of these rare tumors. Similarly, a histological classification is necessary to obtain accurate and specific incidence rates. Financial support: Merck KGgA, Ligues Ain et Rhône, CONTICANET network. No significant financial relationships to disclose.