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Updated: Sep 26 2021

Extra-abdominal Desmoid Tumor

Images mri desmoid 2.jpg tumor.jpg abdominal desmoid tumor.jpg
  • summary
    • Extra-abdominal Desmoid Tumors are benign, locally aggressive, fibrogenic lesions that are associated with familial adenomatous polyposis (FAP).
    • The condition usually presents in patients between the ages of 25 and 35 with a firm, enlarging soft tissue mass
    • Diagnosis is made with a biopsy showing well-differentiated fibroblasts with uniform spindle cells with elongated nuclei and occasional mitoses. Immunohistochemistry will show a positive stain for estrogen receptor-beta.
    • Treatment may be medical management with tamoxifen or wide surgical excision with radiotherapy depending on the size, grade and location of the lesion. 
  • Epidemiology
    • Incidence
      • 900 cases a year in US
    • Demographics
      • younger individuals (25-35 years of age)
      • female>male (3:1)
      • higher incidence in familial adenomatous polyposis (FAP) and Gardner syndrome 4-30%
    • Anatomic location
      • most common shoulder (20%) > chest wall/back (17%) > thigh (13%)
      • >50% are extra-abdominal
      • may have multiple lesions in the same extremity
        • subsequent mass usually appears more proximally in the same limb
      • appears in sites of previous surgery or scars
  • Etiology
    • Genetics
      • patient's with familial adenomatous polyposis (FAP) have increased risk for development of desmoid tumors
        • 15% of tumors have adenomatous polyposis coli (APC) gene mutation (gene controls beta catenin)
        • elevated levels of beta catenin in all tumors
      • trisomy in chromosome 8 or 20
    • Associated conditions
      • Dupuytren contractures
      • Ledderhose disease
      • familial adenomatous polyposis (FAP)
      • Gardner syndrome
  • Symptoms
    • Presentation
      • usually an enlarging mass
      • nerve compression
        • numbness, tingling, motor weakness, stabbing pain
    • Physical exam
      • has a distinctive "rock hard" feel on palpation
        • because tumor is fixed to surrounding tissues
      • poorly circumscribed
      • may be painful and limit motion around joint
  • Imaging
    • Radiographs
      • play minimal role in diagnosis
      • some tumors encroach on/erode bone or trigger periosteal reaction that extends into tumor as "frond like" spicules of bone
    • MRI
      • Indications
        • best means to diagnose
        • exclude multicentric lesions (in the same extremity)
      • findings
        • low signal intensity on T1-weighted images
        • low to medium intensity on T2-weighted images
        • Gadolinium enhances appearance
        • infiltrates muscle
        • 5-10cm in size
        • may erode bone locally
  • Studies
    • Gross specimen
      • gritty
      • white
      • poorly encapsulated
    • Histology
      • Classic characteristics are
        • well-differentiated fibroblasts
        • uniform spindle cells with elongated nuclei and occasional mitoses
        • abundant collagen
        • tumor infiltrates adjacent tissues
    • Molecular Genetics/Immunohistochemisty
      • positive
        • 100% positive for estrogen receptor-beta
        • somatostatin
        • cathepsin D
        • Ki-67
        • c-Kit
      • negative
        • estrogen receptor-alpha
        • progesterone receptor
        • HER2
  • Treatment
    • Nonoperative
      • Watch and wait with serial MRI examinations to monitor for progression
        • tumors may remain stable and even regress over time 
      • low dose-chemotherapy only / tamoxifen
        • indications
          • inoperable lesions
          • tamoxifen favored for failed/poor candidates for standard chemotherapy
            • works because most lesions occur in women and are more aggressive in women, especially premenopausal
            • tamoxifen works via an estrogen receptor blockage
    • Operative
      • wide surgical resection with radiotherapy
        • indications
          • symptomatic lesion
          • recurrent lesion
            • local recurrence is common (reduced recurrence with radiotherapy)
        • external beam radiation dose 50-60Gy
  • Complications
    • Recurrence
      • margin negative
        • 28% recurrence with surgery alone
        • 6% recurence with surgery + radiation
      • margin positive
        • 39% recurence with surgery alone
        • 25% recurernce with surgery + radiation
  • Prognosis
    • High risk of recurrence
    • Highly unpredictable lesions
    • Occasional spontaneous regression
    • No risk of metastasis or malignant transformation, unless related to radiation
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