Desmoid-Type Fibromatosis
Synonyms: Desmoid tumour, deep fibromatosis, aggressive fibromatosis
Watch-and-wait is now first-line management for most asymptomatic lesions
Quick Facts
Behaviour
Intermediate
Category
Soft tissue
Synonyms
- Desmoid tumour
- deep fibromatosis
- aggressive fibromatosis
Category
Soft tissue
Behaviour
Intermediate
Gender
Female
Tissue of Origin
Fibrous
Epidemiology
- Incidence 2–4 per million per year
- Peak incidence in reproductive-age women
- Associated with FAP (familial adenomatous polyposis) in 5–10%
- May be sporadic, post-traumatic, or hormonal
Clinical Features
- Firm, painless or mildly painful deep soft tissue mass
- Progressive growth causing restriction and pain
- Intestinal desmoids in FAP: obstruction, perforation
- Spontaneous regression documented in 20–30%
Location
- Abdominal wall (post-pregnancy most common)
- Intra-abdominal (mesenteric) especially in FAP
- Extra-abdominal: shoulder girdle, chest wall, limbs, head and neck
Imaging
- Well-defined to infiltrative hypointense mass on T1 MRI
- Variable T2 signal (Low in Fibrous areas, High in myxoid areas)
- Enhancement patterns Variable
- CT: Low-density soft tissue mass
Pathology
- Bland spindle cells in abundant collagenous stroma
- Low cellularity, rare mitoses, no necrosis
- Nuclear beta-catenin positivity (IHC)
- CTNNB1 mutation or APC mutation
Genetics
- Sporadic: CTNNB1 (beta-catenin) somatic mutation in 85%
- FAP-associated: APC germline mutation
- T41A, S45F, S45P mutations associated with worse recurrence risk
- No recurrent chromosomal alterations
Treatment
- Active surveillance (watch and wait) - first-line for asymptomatic stable lesions
- Sorafenib or pazopanib - most active systemic agents
- Imatinib - activity in PDGFR-expressing tumours
- Surgery - reserved for symptomatic/progressive lesions with achievable clear margins; High recurrence rate
- Radiotherapy for unresectable or recurrent disease
Prognosis
- No Malignant potential - does not metastasise
- Local recurrence remains the major problem (30–70% after surgery)
- Spontaneous regression in 20–30% - supports watchful waiting
- FAP-associated intra-abdominal desmoids: Higher morbidity and mortality
Key Points
- Watch-and-wait is now first-line management for most asymptomatic lesions
- CTNNB1 mutation type predicts recurrence risk
- Screen for FAP when intra-abdominal/mesenteric desmoid is diagnosed
- Sorafenib is currently the most active systemic treatment based on RCT data
Workup - Blood Tests
- FBC, U&E, LFTs - baseline
- CTNNB1 mutational status from biopsy tissue - T41A/S45F predicts recurrence risk
- APC germline testing if intra-abdominal/mesenteric location (FAP association)
Workup - Local Imaging
MRI primary site - first-line; T1/T2 characteristics; infiltrative margins
Workup - Biopsy
- Core needle biopsy - confirm before treatment; avoid surgery without biopsy
- IHC: nuclear beta-catenin+ (CTNNB1 mutation)
- CTNNB1 mutational analysis (Sanger sequencing) - T41A/S45F carry Higher recurrence risk
- Exclude sarcoma and fibrosarcoma with IHC panel
Workup - Staging
CT abdomen/pelvis for intra-abdominal desmoids - assess bowel/ureter involvement
Workup - Other
- Genetics referral if mesenteric/intra-abdominal location - colonoscopy surveillance for FAP
- MDT at soft tissue sarcoma centre - watch-and-wait is now first-line for asymptomatic stable lesions
Follow-up Summary
- 1
Active surveillance (watch-and-wait)
MRI primary site at 3 and 6 months, then 6-monthly for 2 years, then annually
- 2
Post-surgical
MRI at 3 months, 6 months, then 6-monthly to 5 years; annual MRI to 10 years
- 3
Sorafenib/imatinib therapy
imaging response assessment at 3–6 months; toxicity review at each visit
- 4
No systemic metastatic risk - no CT chest surveillance required
- 5
FAP/APC germline mutation
refer to genetics; colonoscopy surveillance mandatory
- 6
CTNNB1 mutation type (T41A, S45F) may guide recurrence risk stratification
- 7
Discharge at 10 years if stable; intra-abdominal desmoids may warrant continued MDT review
Medical disclaimer
The content on Sarcopedia is for educational and informational purposes only and does not constitute medical advice. It is not intended to be a substitute for professional medical diagnosis or treatment. Always consult with a qualified physician regarding any health concerns or before starting any new treatment. Reliance on any information provided on this site is solely at your own risk.