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Updated: Jun 22 2021

Intramuscular Myxomas


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Images myxoma.jpg 2.jpg intramuscular myxoma.jpg
  • summary
    • Intramuscular Myxomas are benign soft tissue tumors that present as slow-growing deeply seated masses confined within the skeletal muscle.
    • The condition is typically seen in patients between 40 and 60 years of age who present with a slow-growing mass that may or may not be painful.
    • Diagnosis is made with MRI studies showing a homogenous mass with an intramuscular location.
    • Treatment is observation for asymptomatic lesions. Marginal surgical excision is indicated for symptomatic lesions that do not resolve with nonoperative management. 
  • Epidemiology
    • Demographics
      • occur in 40 to 60 year olds
      • slight female predilection
    • Associated conditions
      • commonly located in the thigh, shoulder, buttock, or upper arm
  • Etiology
    • Mechanism
      • likely develop from premature mesenchymal stem cells which differentiate into benign fibroblasts which loose their capacity to secrete collagen
    • Associated conditions
      • Mazabraud's syndrome
        • a syndrome characterized by multiple intramuscular myxomas associated with monostotic or polyostotic fibrous dysplasia
      • myxoid liposarcomas
        • important to differentiate from a myxoid liposarcomas, which occurs in an intermuscular location
  • Presentation
    • Symptoms
      • slowly growing mass
      • may or may not be painful
        • pain in soft tissue sarcomas is often based on compression of surrounding tissues like vessels or nerves
  • Imaging
    • MRI
      • homogeneous appearance
      • bright T2 signal
      • dark T1 signal
      • intramuscular location
        • intramuscular location of myxomas is important to differentiate from myxoid liposarcoma, which occurs in an intermuscular location
  • Studies
    • Histology
      • characterized by bland and hypo-cellular myxoid stroma
      • no cellular atypia
      • low nuclear to cytoplasmic ratio
      • no atypical mitosis
  • Treatment
    • Nonoperative
      • observation
        • indications
          • for asymptomatic lesions
    • Operative
      • marginal surgical excision
        • indications
          • symptomatic benign low-grade tumors
        • neoadjuvant chemo-radiotherapy is not needed
        • local recurrence and metastasis uncommon
  • Prognosis
    • Local recurrence and metastasis uncommon
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