br Conclusions br Author contribution br Funding
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Introduction Sarcomas are rare malignant neoplasms that develop from mesenchymal cells; they represent approximately 1% of all cancers and include a heterogeneous group of more than 70 different histological subtypes that may arise at any anatomical site [, , , , , , ]. Therefore, both topography and morphology contribute to the heterogeneity of sarcomas. In most cases, risk factors for sarcoma are unclear, although exposure to ionising LLY507 has increased the risk of soft tissue sarcoma (STS) . Current estimates suggest that radiotherapy-associated sarcomas account for only 3–6% of all sarcomas [, , ]. Primary radiation-related STS, rather than sporadic disease, has been associated with significantly worse disease-specific survival . Other potential risk factors for sarcomas include chemical exposure to herbicides (e.g. phenoxyacetic acids), wood preservatives (e.g. those containing chlorophenols), chronic lymphedema (Stewart–Treves syndrome) and inherited conditions such as neurofibromatosis-1, retinoblastoma and Li-Fraumeni syndrome [6,10]. STS comprise ≈70‒80% of sarcomas [1,3] and are one of the main groups of cancers among rare cancers . The significant anatomical and histological heterogeneity of STS means it is often difficult for healthcare professionals to acquire the levels of expertise required for appropriate management of each different STS subtype . In addition, epidemiological data on specific STS subtypes are limited, and there are concerns about data quality regarding STS subtype in population-based cancer registries. The difficulties in making an exact diagnosis by pathologists, together with possible registration bias, could lead to a high proportion of poorly specified STS histological subtypes, which in turn could lead to a possible underestimation of the incidence of specific STS subtypes . Published articles focusing on STS epidemiology in Italy are lacking. Thus, an important aim of myofibrils review is to bring together all data available in Italy and other EU countries to provide more accurate epidemiological data to healthcare policy makers and other stakeholders in Italy and elsewhere, and to provide a synthesis of these data, which may lead to improved patient care and clinical outcomes. Additional, definitive aims of the review are to raise awareness about STS and the importance of registries, and to focus on the importance of multidisciplinary management in referral centres. These aims are also in line with expert-panel recommendations, such as those from the Sarcoma Policy Checklist (Table 1) . The review compares epidemiological data from the population-based Italian Association of Cancer Registries (AIRTUM)  with data from population-based studies from Europe: the Connective Tissue Cancer Network (CONTICANET) , the Surveillance of Rare Cancers in Europe (RARECARE) Working Group , the Information Network on Rare Cancers (RARECAREnet) [16,17], and rare cancers in Italy (RITA) .
Incidence and prevalence of STS in Italy compared with other European countries Incidence, which quantifies the number of new cases with sarcoma and therefore is a good proxy of the disease burden posed by patients requiring first-line treatment, is considered a more appropriate indicator of tumour rarity than prevalence. Indeed, incidence can be used to indicate the number of patients with a specific condition that may be relevant for statistical design considerations in clinical trials. Although any threshold for definition of tumour rarity should be regarded as indicative only, the RARECARE expert group defined rare cancers as those occurring with an annual incidence of fewer than six cases per 100,000 [1,6,13]. Overall, rare cancers account for approximately 24% of all cancers in Europe [1,13,17]. STS represent <1% of all cancers [3,19] but are among the rare cancers with the highest incidence .