However the diagnostic misclassification of STS might be
However, the diagnostic misclassification of STS might be another explanation for differences between AIRTUM and RARECAREnet data, considering that diagnostic discrepancy between pathologists may occur in up to 30% of cases . Additionally, some of this difference may have resulted from variation in registration practices for Luteolin cancers. Also of note is that RARECAREnet reported some inter-regional variability in age-standardised incidence rates of STS: rates were greatest in southern Europe (including Italy; 4.26 cases per 100,000 per year), central Europe (4.18), and Ireland and the UK (4.03) and lowest in northern Europe (3.89) and eastern Europe (3.78) .
CONTICANET was a population-based prospective study that collected epidemiological data about sarcomas over 2 years from two regions in France and one in Italy (2005–2006 in Rhone-Alpes and 2007–2008 in Aquitaine and Veneto), and included more than 26 million person-years of observation . Patients had to be residents in the region and were identified by the regional network of pathologists, although experts in second opinions for sarcoma in each region supported the study and reviewed the diagnoses of local pathologists. Thus, while AIRTUM  and RARECAREnet [16,17] provide population-based registry data, CONTICANET  does not. More importantly, whereas AIRTUM and RARECAREnet used the same anatomical sites and ICD-O-3 morphology, CONTICANET did not use the same anatomical sites. Therefore, methodological differences make meaningful comparison of data from CONTICANET with those from AIRTUM and RARECAREnet difficult. For example, in CONTICANET, 968 of 1558 cases (62%) were defined as STS and 590 (38%) were defined as visceral sarcomas. The CIR for overall STS (regardless of site of origin) in CONTICANET was 5.76 per 100,000 per year ; overall STS CIRs for Italy  and Europe [16,17] were 6.27 and 4.71 per 100,000 per year, respectively.
Histological subtypes of STS In the CONTICANET project, the most frequent histotypes of STS were liposarcoma (26.2% of cases), leiomyosarcoma (16.1%), and dermatofibrosarcoma protuberans (10.1%); the CIR for liposarcoma was 0.94 cases per 100,000 population per year, with dedifferentiated liposarcoma being the most common subset (0.24 cases per 100,000 per year) . In males, the most frequent STS histotypes were liposarcoma (22%) and leiomyosarcoma (11%); in females, the most frequent STS histotypes were leiomyosarcoma (21%) and liposarcoma (13%) . Interestingly, in the Rhone-Alpes region, data revealed a younger peak age incidence for well-differentiated liposarcoma (60–69 years) than dedifferentiated liposarcoma (80–89 years) . In the RARECARE project, the most frequent STS histotypes were leiomyosarcoma, which accounted for 20% of all sarcomas, then unspecified sarcoma (18%), and liposarcoma (10%) . Although these results may be somewhat unexpected in that liposarcoma was not the most frequent STS histotype, these findings may be explained by several factors . The female STS population included a large proportion of uterine leiomyosarcomas. Overall, 24% of leiomyosarcomas arose in the uterus, which highlights a pressing need for pathological reclassification of uterine sarcomas. In addition, not all GIST diagnosed as leiomyosarcomas may have been recorded as originating from the gastrointestinal tract, as some cases may have been reported as retroperitoneal or pelvic in origin. Also, some leiomyosarcomas may now be classified as pleomorphic sarcomas with a myogenic differentiation that is insufficient to make them true leiomyosarcomas. RARECARE also had a relatively high proportion of unspecified sarcomas (18%), which would have contributed to a lower incidence of specific histological subtypes of STS . Of note, in France, the Reference Network for Pathology of Soft Tissue-GIST-Desmoid-Visceral Sarcomas (RRePS) has undertaken the systematic histopathologic review of all newly diagnosed cases of sarcoma, GIST, and desmoid tumours and estimated the following distribution of STS by histotype: liposarcoma (25.2% of cases), undifferentiated pleomorphic sarcoma (21.8%), leiomyosarcoma (17.1%), myxofibrosarcoma (5.8%), angiosarcoma (5.0%), rhabdomyosarcoma (5%), synovial sarcoma (4.2%), malignant peripheral neural sheath tumours (2.6%) and others (13.3%) [22,23].