Proliferative Myositis
Original Editors - Billie Rehberg from Bellarmine University's Pathophysiology of Complex Patient Problems project.
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Definition/Description [edit | edit source]
Proliferative myositis (PM) is a benign tumor which grows in skeletal muscle[1]. It is usually 3-4 cm in diameter[2], and is often mistaken for sarcomas (especially rhabdomyosarcoma)[3]. The tumor is formed by ganglion-like cells, fibroblasts, and myofibroblasts which increase the spaces between muscle fibers[2]. While etiology is unknown, it may result from injury to the muscle, fascia, or vasculature (resulting in ischemia) of the associated area[4]. PM generally presents in the upper extremity or trunk regions[2]. Median age of onset is 50 years[5], with rare cases reported in children[2]. [Photo: PM of the SCM muscle[1]]
Prevalence
[edit | edit source]
According to an article written by Fauser et. al in 2008, approximately 100 cases of PM had been published in the literature[1]. According to Jassar and Kumar (2005), approximately 1000 cases have been reported[6].
Characteristics/Clinical Presentation[1][6] [edit | edit source]
- Rapidly enlarging, solid tumor within skeletal muscle
- Localized inflammation
- No lymph node enlargement
- No significant laboratory results
- Possible localized pain
[Photo: Computerized Tomography of PM of the SCM muscle[1]]
Associated Co-morbidities[edit | edit source]
No associated co-morbidities have been reported.
Medications[edit | edit source]
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Diagnostic Tests/Lab Tests/Lab Values[edit | edit source]
Proliferative Myositis is diagnosed based on biopsy[1]. The following list, taken directly from the Stanford University School of Medicine page on PM, are histologic and immunologic characteristics of PM which are used in its diagnosis:
o Relatively normal muscle fibers separated by expanded myxoid connective tissue
o Produces distinctive checkerboard pattern
o No evidence of muscle damage
o No sarcolemmal proliferation
o No multinucleation
o No nuclear enlargement
o No necrosis
o Connective tissue space between fibers contains reactive cells resembling those seen in nodular fasciitis and proliferative fasciitis
o Spindled and stellate fibroblasts and myofibroblasts
o Vesicular nuclei
o No cytologic atypia
o Actin positive
o CD68 variable
o S100, desmin negative
o Ganglion-like cells
o Characteristic feature of this process
o Large round regular nuclei
o Occasional binucleate and trinucleate cells may be seen
o Prominent nucleoli
o Dispersed chromatin
o Basophilic to amphophilic cytoplasm
o May be clustered and may mold each other
o Factor XIIIa positive
o Actin, CD68 negative to focal/weak
o Desmin, keratin, S100, neuron specific enolase negative
o Mitotic figures frequent
o No atypical mitotic figures [2]
Etiology/Causes[edit | edit source]
While etiology is unknown, PM may result from injury to the muscle, fascia, or vasculature (resulting in ischemia) of the associated area[4].
Systemic Involvement[edit | edit source]
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Medical Management (current best evidence)[edit | edit source]
Proliferative Myositis is a self-limiting pathology, meaning that the growth of the tumor will eventually stop. While spontaneous resolution of the tumor has been reported[1], surgical excision is the only treatment and recurrence following excision is rare[2].
Physical Therapy Management (current best evidence)[edit | edit source]
It has been theorized that PM is a precursor to heterotopic ossification or myositis ossificans[6]. Thus, aggressive range of motion and strengthening exercises should be avoided to prevent possible aggravation of the condition while the tumor is still enlarging. ROM and strengthening exercises and modalities to regain normal muscular function and decrease pain following surgery may be indicated.
Alternative/Holistic Management (current best evidence)[edit | edit source]
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Differential Diagnosis[5][3][2][edit | edit source]
- Myositis Ossificans
- Neoplasms (especially rhabdomyosarcomas)
- Proliferative fasciitis
- Nodular fasciitis
- Fibromatosis
- Ganglioneuroblastoma or ganglioneuroma
Case Reports/ Case Studies[edit | edit source]
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Resources
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Recent Related Research (from Pubmed)[edit | edit source]
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References[edit | edit source]
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- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Fauser C, Nahrig J, Niedermeyer H, Arnold W. Proliferative myositis: a rare pseudomalignant tumor of the head and neck. Archives of Otolaryngology - Head & Neck Surgery [serial on the Internet]. (2008, Apr), [cited March 16, 2011]; 134(4): 437-440. Available from: CINAHL with Full Text.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Stanford University. Proliferative Myositis. Available at http://surgpathcriteria.stanford.edu/softfib/proliferative_myositis/printable.html. Accessed April 4, 2011
- ↑ 3.0 3.1 Meis J, Enzinger F. Proliferative fasciitis and myositis of childhood. The American Journal Of Surgical Pathology [serial on the Internet]. (1992, Apr), [cited March 16, 2011]; 16(4): 364-372. Available from: MEDLINE.
- ↑ 4.0 4.1 Dent C, DeBoom G, Hamlin M. Proliferative myositis of the head and neck. Report of a case and review of the literature. Oral Surgery, Oral Medicine, And Oral Pathology [serial on the Internet]. (1994, Sep), [cited March 16, 2011]; 78(3): 354-358. Available from: MEDLINE.
- ↑ 5.0 5.1 Mulier S, Stas M, Delabie J, Lateur L, Gysen M, De Wever I, et al. Proliferative myositis in a child. Skeletal Radiology [serial on the Internet]. (1999, Dec), [cited March 16, 2011]; 28(12): 703-709. Available from: MEDLINE.
- ↑ 6.0 6.1 6.2 Jassar A, Kumar V. Proliferative myositis--a case report. Indian Journal Of Pathology & Microbiology [serial online]. January 2005;48(1):33-35. Available from: MEDLINE, Ipswich, MA. Accessed April 5, 2011.