Desmoid-Type Fibromatosis
Synonyms: Desmoid tumour, deep fibromatosis, aggressive fibromatosis
Locally aggressive, non-metastasising fibroblastic neoplasm
Quick Facts
Behaviour
Intermediate
Category
Soft tissue
Synonyms
- Desmoid tumour
- deep fibromatosis
- aggressive fibromatosis
Category
Soft tissue
Behaviour
Intermediate
Gender
Female (2:1)
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
- Extra-abdominal: shoulder, chest, limbs (60%)
- Abdominal wall (post-pregnancy most common) (25%)
- Intra-abdominal (mesenteric) especially in FAP (15%)
Imaging
- MRI: Well-defined to infiltrative hypointense mass on T1
- Variable T2 signal (low in fibrous areas, high in myxoid areas). Enhancement patterns variable
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
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
- Locally aggressive, non-metastasising fibroblastic neoplasm
- Relentless local infiltration and a high propensity for recurrence
- Watch-and-wait is now first-line management for most asymptomatic/stable 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
Workup - Blood Tests
- FBC, U&E, LFTs - baseline
- APC germline testing if intra-abdominal/mesenteric location (FAP association)
Workup - Local Imaging
MRI with contrast of primary site
Workup - Biopsy
Core needle biopsy
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
- MDM discussion at a sarcoma centre
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
Discharge at 10 years if stable; intra-abdominal desmoids may warrant continued MDT review
Medical disclaimer
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