This study will be a multi-institutional, prospective, observational study of patients with localized primary AS of any site within ISG and RTR centers. Patients will be treated according to clinical practice of the center and according to ISG clinical recommendations on localized AS.

The management of localized AS remains a clinical challenge and needs to be better defined and standardized, especially with regards to the role of radiation-therapy and systemic treatment. Several questions about the best treatment approach to some clinical presentations remain open and would need to be answered by clinical studies. Unfortunately, the rarity of this histology among sarcomas makes it challenging to carry out clinical studies in all such presentations. Moreover, prognostic factors are lacking and differences in epidemiological, pathological and clinical aspects between primary AS and secondary AS need to be better characterized.

These issues may be addressed with a prospective multi-institutional observational study, through the collection of clinical and pathological data of patients with localized AS.

Involving all reference centres for sarcoma in Italy, the Italian Sarcoma Group (ISG) will be the ideal network for this study, with the collaboration of the Italian Rare Cancer Network (RTR), a 7collaborative network among Italian centres focusing on improving the quality of care of patients with rare tumors.

Inclusion Criteria:

• pathological diagnosis of AS;
• any site of origin;
• any age;
• primary, localized, resectable disease.

Exclusion Criteria: NA

• pathological diagnosis of AS;
• any site of origin;
• any age;
• primary, localized, resectable disease.