Introduction
Desmoid-type aggressive
fibromatosis (AF), also known as desmoid tumor, is a rare, fibroblastic, locally
invasive neoplasm with no metastatic potential but with a high recurrence rate.
Although histologically benign, it often behaves aggressively by infiltrating
surrounding structures, leading to significant morbidity. Among the
extra-abdominal forms, the gluteal region
is a recognized but relatively uncommon site. This article offers an expert-level review of gluteal desmoid-type aggressive fibromatosis, with a focus on its cause, etiology, pathophysiology, epidemiology, clinical presentation, imaging features, treatment options, and prognosis. All imaging findings are directly referenced from the
provided case study of a 42-year-old woman with swelling in the right gluteal area.
Cause and Etiology
The etiology of
desmoid-type fibromatosis is multifactorial and involves both
genetic and environmental influences.
1.
Genetic Factors:
o Mutations in the CTNNB1 gene
(encoding β-catenin) are the most common sporadic mutations.
o Patients with familial adenomatous polyposis
(FAP) and Gardner’s syndrome
carry germline APC gene mutations, predisposing
them to desmoid tumors.
2.
Hormonal Factors:
o Estrogen plays a role in tumor growth, explaining its predilection
for women of reproductive age.
3.
Trauma and Surgery:
o Local trauma, previous surgery, or even childbirth can trigger
abnormal fibroblastic proliferation.
Pathophysiology
Desmoid tumors arise from
clonal proliferation of myofibroblasts.
The hallmark is dysregulated Wnt/β-catenin signaling,
leading to persistent fibroblastic proliferation and excess collagen
deposition. Unlike sarcomas, desmoid tumors do not metastasize, but their
infiltrative nature leads to destruction of muscles, tendons, and adjacent
bones.
·
Histology: Spindle-shaped fibroblasts in a collagen-rich stroma.
·
Molecular Signature: Nuclear β-catenin accumulation.
·
Growth Behavior: Phases of progression, stabilization, and possible regression.
Epidemiology
·
Incidence: ~2–4 cases per
million annually.
·
Gender: More common in females
(2–3:1 ratio).
·
Peak age: 20–40 years.
·
Sites: Extra-abdominal forms
commonly affect extremities, chest wall, head and neck, breast, and gluteal
region.
Clinical Presentation
In the presented case, a 42-year-old woman developed right
gluteal swelling.
·
Patients typically present
with:
o A painless, slow-growing mass
o Local discomfort or fullness
o Limited mobility if adjacent muscles or joints are involved
o Neurological symptoms if nerves are compressed
Unlike malignant tumors,
systemic features such as fever or weight loss are absent.
Imaging Features
MRI is the imaging modality
of choice. The attached case demonstrates classical findings:
 |
| [Figure 1] Coronal STIR: High signal intensity mass deep to the right gluteal muscles. |
 |
| [Figure 2] Coronal T2 Weighted: Heterogeneous T2 signal with internal low-signal bands (“band sign”). |
 |
| [Figure 3] Coronal T1 Weighted: Isointense to muscle with infiltrative margins. |
 |
| [Figure 4]Axial T1 Weighted: Mass smoothly abutting the proximal femoral shaft. |
 |
| [Figure 5] Axial STIR: Hyperintensity with better lesion conspicuity. |
 |
| [Figure 6] Axial T2 Weighted: Heterogeneity with hypointense fibrous bands. |
 |
| [Figure 7] Axial T1 Contrast: Moderate enhancement in cellular components. |
 |
| [Figure 8] Axial DWI: Restricted diffusion is not prominent, differentiating it from high-grade sarcoma. |
 |
| [Figure 9] Axial c+ fat sat: Enhancing cellular areas with split-fat sign. |
 |
| [Figure 10] Sagittal T1: Soft tissue infiltration across fascial planes. |
 |
| [Figure 11] Sagittal T1 c+: Heterogeneous enhancement pattern. |
Key MRI Signs
·
Band sign: Low-signal collagenous bands on all sequences.
·
Split-fat sign: Rim of fat surrounding the lesion.
·
Variable enhancement: Cellular regions enhance more than fibrotic zones.
Treatment
The management strategy has
evolved from aggressive surgical resection to a more individualized,
multidisciplinary approach:
1.
Active Surveillance
(“Wait-and-See”):
o Many desmoid tumors remain stable or regress spontaneously.
o First-line management for asymptomatic patients.
2.
Surgery:
o Once considered standard, now reserved for symptomatic or
progressive cases.
o High recurrence rates (20–40%), especially in gluteal locations where
complete excision is difficult.
3.
Radiotherapy:
o Useful for unresectable or recurrent lesions.
o Provides local control but risk of late radiation-induced morbidity.
4.
Systemic Therapy:
o NSAIDs (e.g., sulindac) and anti-estrogen agents (tamoxifen)
are used in hormonally sensitive cases.
o Tyrosine kinase inhibitors (sorafenib, imatinib,
pazopanib) show promising results in clinical
trials.
o Chemotherapy (methotrexate + vinblastine or
doxorubicin-based regimens) for aggressive or
refractory disease.
Prognosis
·
Metastasis: None (histologically benign).
·
Recurrence: High local recurrence, particularly after incomplete resection.
·
Quality of life: Major morbidity from local invasion (e.g., chronic pain, impaired
mobility).
·
Overall outlook: With modern conservative strategies, survival is excellent, but
long-term follow-up is mandatory.
Quiz
1.
Which of the following genetic
mutations is most frequently associated with sporadic desmoid-type fibromatosis?
a) TP53
b) CTNNB1
c) RB1
d) BRCA1
2.
Which MRI feature is considered
highly characteristic of desmoid-type fibromatosis?
a) Homogeneous high T2 signal
b) Multiple cystic areas
c) Low-signal intensity bands on all sequences (“band sign”)
d) Peripheral calcification
3.
What is the current recommended
first-line management for asymptomatic extra-abdominal desmoid fibromatosis?
a) Immediate surgical excision
b) High-dose chemotherapy
c) Active surveillance (“wait-and-see”)
d) Radiotherapy
Answer & Explanation
1. Answer: b) CTNNB1. Explanation: Sporadic desmoid tumors are most commonly
linked to activating mutations in the CTNNB1 gene, leading to β-catenin
stabilization.
2. Answer: c) Low-signal intensity bands on all sequences. Explanation: The
“band sign” corresponds to dense collagen stroma, a hallmark MRI feature of
desmoid fibromatosis.
3. Answer: c) Active surveillance. Explanation: Many tumors remain indolent or regress spontaneously, so initial observation is now the standard approach.
References
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[4] G. Fiore et al., “Desmoid-type fibromatosis: evolving treatment standards,”
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803–826, 2016.
[5] C. Toulmonde, “Sorafenib in advanced and refractory desmoid tumors: a phase
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versus conservative approach,” Journal of Surgical Oncology,
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