Intramuscular Myxomas


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

TAG

(OBQ09.255) A 40-year-old male presents to your office with complaints of hip/leg pain for 6 months. He is otherwise healthy and denies trauma. Radiographs, MRI, and histology images are shown in figures A through D. What treatment do you suggest for this patient? Topic

Review Topic

FIGURES: A

1. Observation
2. Physical therapy
3. Surgical excision
4. Neoadjuvant chemotherapy followed by surgical excision
5. Surgical excision followed by adjuvant radiotherapy

PREFERRED RESPONSE ▶

DISCUSSION: The history and images suggest an intramuscular myxoma, a benign tumour that presents as a slow growing deeply seated mass confined to the skeletal muscle.

The keys to this question are the 1) intramuscular location, 2) relatively homogenous appearance on MRI, 3) bright T2/dark T1 signal - suggesting a myxoid tumor, and 4) bland, hypo-cellular myxoid appearing histology that does not show cellular atypia in the relatively homogenous cells without nuclear atypia, mitotic figures, or high nuclear to cytoplasmic ratio.

As described in the referenced review by Prado et al. local surgical excision is the treatment of choice and recurrence is extremely rare. Intramuscular myxomas are commonly located in the thigh, shoulder, buttock, or upper arm. Multiple intramuscular myxomas are usually associated with monostotic or polyostotic fibrous dysplasia, also known as Mazabraud's syndrome.

REFERENCES:

1. Prado MA, Miró RL, Leal IM, Vargas J, Dorrego EJ. Intramuscular myxoma: differential diagnosis and review of the literature. Orthopedics. 2002 Nov;25(11):1297-9. Review. PMID:12452352 (Link to Abstract)

2. Schwartz HS (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors 2. American Academy of Orthopaedic Surgeons, Rosemont, IL. 2007, pp 257-263

Question Authors:

Patrick O'Donnell MD/PhD, Michael Hughes MD,

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Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Prado MA, Miró RL, Leal IM, Vargas J, Dorrego EJ. Intramuscular myxoma: differential diagnosis and review of the literature. Orthopedics. 2002 Nov;25(11):1297-9. Review. PMID:12452352 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Schwartz HS (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors 2. American Academy of Orthopaedic Surgeons, Rosemont, IL. 2007, pp 257-263

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