Desmoid tumors are slow-growing, mostly benign but locally aggressive tumors caused by the proliferation of fibroblasts. They are often associated with familial adenomatous polyposis and can arise from any part of the body, most commonly the extremities, abdominal wall, and the abdominal cavity. Individuals may be asymptomatic until the tumors grow large enough to compress adjacent structures (e.g., bowel obstruction). Diagnosis includes imaging and requires biopsy with immunohistochemistry for confirmation. Treatment is based on active surveillance with MRI.
- Beta-catenin/WNT (CTNNB1 gene) mutation: associated with sporadic development of desmoid tumors (∼ 85 %) 
- APC gene mutation: associated with (FAP), specifically (∼ 15 %)
- Hyperestrogenic states (e.g., during or following a pregnancy, oral contraceptives use, IVF)
- Repeated trauma (e.g., surgical procedures)
According to etiology
According to location
- Imaging: shows infiltration of muscles, deep tissue, and along muscle planes 
- Core needle biopsy (definitive diagnosis) 
- Other: Colonoscopy and germline testing should be considered if is suspected.
- First-line 
Alternatives: Active treatment should be considered only in persistent progression.
- Surgical intervention: sporadic desmoid tumors localized in the abdominal wall
- Medical therapy: sporadic desmoid tumors localized at all other sites and for progressive FAP-associated desmoid tumors
- Local ablative treatments (e.g., radiotherapy, cryotherapy): determined on an individual basis
- Desmoid tumors are locally aggressive and associated with a high local recurrence rate but lack metastatic potential.
- Unpredictable clinical course (from spontaneous regression to progression and stable chronic disease)
- Desmoid tumors may compress vital organs and disrupt their function with potentially fatal consequences.