This observational study aims to characterize the molecular, phenotypic, and functional inflammatory and immunological profile of patients with sporadic desmoid-type fibromatosis undergoing either active surveillance or systemic therapy. The study includes analysis of the tumor immune microenvironment (TIME), circulating immune and inflammatory molecules, immune cell subsets, and circulating tumor DNA (ctDNA). The goal is to identify biomarkers associated with spontaneous or treatment-induced tumor regression and to evaluate potential correlations with specific ß-catenin mutations.

Inclusion Criteria:

• Patients with primary sporadic desmoid-type fibromatosis with measurable disease under active surveillance
• Patients with primary sporadic desmoid-type fibromatosis with measurable disease receiving systemic treatment.

• Patients with primary sporadic desmoid-type fibromatosis with measurable disease under active surveillance
• Patients with primary sporadic desmoid-type fibromatosis with measurable disease receiving systemic treatment.

Aggregated clinical and molecular data generated from the study will be shared in scientific publications and presentations. These aggregated data will be made available after the publication of the main study results. Aggregated data will become available after publication of the primary results after the end of the study. Aggregated data will be available to researchers and clinicians through scientific publications and conference communications for scientific, educational, and research purposes, including further understanding of desmoid-type fibromatosis biology and clinical behavior. Data will be shared through peer-reviewed publications, conference presentations, and other scientific dissemination channels.