Intramuscular Myxomas - Pathology


Introduction
Benign soft tissue tumor that presents as a slow growing deeply seated mass confined within the skeletal muscle (intramuscular) myxo from greek means mucus likely develop from premature mesenchymal stem cells which differentiate into benign fibroblasts which loose their capacity to secrete collagen Epidemiology demographics occur in 40 to 60 year olds slight female predilection associated conditions commonly located in the thigh, shoulder, buttock, or upper arm 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 Prognosis local recurrence and metastasis uncommon
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