Desmoid tumor (DT) of the abdomen is a challenging and rare disease. The level of evidence available to document their treatment is relatively low, however, recent publications of prospective studies have allowed to precise their management.
This document is a summary of the French intergroup guidelines realized by all French medical and surgical societies involved in the management of DT located in the abdomen or associated with adenomatous polyposis. Recommendations are graded in four categories (A, B, C and D), according to the level of evidence found in the literature until January 2021.
When the diagnosis of DT is suspected a percutaneous biopsy should be performed when possible. A molecular analysis looking for pathogenic mutations of the CTNNB1 and APC genes should be systematically performed. When a somatic pathogenic variant of the APC gene is present, an intestinal polyposis should be searched. Due to a high rate of spontaneous regression, non-complicated DT should first benefit from an active surveillance with MRI within 2 months after diagnosis to assess the dynamic of tumor growth. The treatment decision must be discussed in an expert center, favoring the less toxic treatments which can include broad spectrum tyrosine kinase inhibitor or conventional chemotherapy (methotrexate-vinblastine). Surgery, outside the context of emergency, should only be considered for favorable location in an expert center.
French guidelines for DT management were elaborated to help offering the best personalized therapeutic strategy in daily clinical practice as the DT therapeutic landscape is complexifying. Each individual case must be discussed within a multidisciplinary expert team.

Desmoid-type fibromatosis (DF) is a rare monoclonal, fibroblastic proliferation characterised by a variable and often unpredictable clinical course. It may affect nearly all parts of the body including extremities, trunk and abdomen. Considering the variable clinical presentations, anatomic locations and biological behaviours, an individualised treatment approach is required. No established or evidence-based approach for the treatment of this neoplasm is available as of today. Therefore, we propose a consensus treatment algorithm based on a round table meeting bringing together sarcoma experts from the European Organisation for Research and Treatment of Cancer (EORTC) Soft Tissue and Bone Sarcoma Group (STBSG) with patient advocates from Sarcoma Patients EuroNet (SPAEN). The aim of the meeting was to develop - for the first time ever - a consensus approach based on professionals\' AND patients\' expertise. As a fundamental prerequisite, all patients should be discussed in a multidisciplinary setting in centres or professional networks with a specific expertise in the disease.