Tailored Beta-catenin Mutational Approach in Extra-abdominal Sporadic Desmoids Tumor Patients

This is a prospective, multicenter observational study under the umbrella of the ISG (Italian Sarcoma Group) evaluating local progression-free survival at 3 years of patients affected by extra-abdominal primary fibromatosis managed with front-line conservative approach and treated only in case of demonstrated progressive disease. All patients included will be placed on wait and see approach and then shifted to treatment in case of documented radiological progressive disease. For patient primarily evaluated for suspected desmoid tumor, a core-needle biopsy (eventually under CT/ultrasound guide) will be obtained for histological diagnosis and mutational analysis of CTNNB1 exon 3 (gene encoding Beta-catenin). If incisional biopsy or surgical procedure has done elsewhere, samples will be requested for histological confirmation and mutational analysis (centralization at the investigators Institution). In case of progression at 3 months, defined as tumor growth documented radiologically (by contrast enhanced MRI) by Response Evaluation Criteria in Solid Tumors (RECIST), administered treatments will be proposed and then registered in the clinical database.The choice of the treatment and eventually the possibility of continuation of " surveillance only" will be at the discretion of Institution's Multidisciplinary Sarcoma Committee or as part of clinical trials with the consent of patient.