DOI: 10.1148/radiol.2442041504
(Radiology 2007;244:613-616.)
© RSNA, 2007
Case 118: Proliferative Myositis1
Mustafa Kemal Demir, MD2,
Mahmut Beser, MD and
Okan Akinci, MD
1 From the Department of Radiology, Haydarpasa Numune Education and Research Hospital (M.K.D., O.A.), Istanbul, Turkey; and Department of Radiology, Taksim Education and Research Hospital, Istanbul, Turkey (M.B.). Received August 31, 2004; revision requested November 8; revision received December 2; accepted December 17; final version accepted January 27, 2005.
Correspondence: Address correspondence to M.K.D., 11 kisim, Yasemin Apt, D blok, Daire 35 Ataköy, Istanbul, Turkey 34158 (e-mail: demirkemal{at}superonline.com).
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HISTORY
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A 65-year-old woman with no relevant medical or surgical history presented to the orthopedic clinic with a 3-week history of a painful mass in her right arm that manifested 1 week after trauma. Physical examination revealed a firm palpable mass in the right biceps muscle, without overlying skin changes. She was afebrile. Laboratory studies did not reveal any abnormalities. Conventional radiography (images not shown) depicted a soft-tissue mass, without any soft-tissue calcification or skeletal abnormality. Magnetic resonance (MR) imaging was performed.
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IMAGING FINDINGS
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MR imaging of the right upper extremity revealed a well-defined soft-tissue mass (7.0 x 3.5 x 3.0 cm) in the belly of the right biceps muscle. The lesion had high signal intensity on fat-saturated T2-weighted spin-echo sagittal (Fig 1a) and coronal (Fig 1b) MR images, had moderately high signal intensity on a transverse T2-weighted gradient-echo MR image (Fig 2), and was isointense compared with the signal intensity of skeletal muscle on a T1-weighted sagittal spin-echo MR image (Fig 3). Imaging performed after intravenous administration of gadopentetate dimeglumine (Magnevist; Schering, Berlin, Germany) revealed almost homogeneous enhancement of the mass (Fig 4). The T2-weighted and contrast-enhanced MR images also demonstrated continuous muscle fibers without disruption in the lesion. There was no infiltration of soft tissues surrounding the involved muscle on any images. The osseous structures demonstrated normal morphologic and signal intensity characteristics with all imaging sequences.
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Figure 1a: Oblique (a) sagittal and (b) coronal fat-saturated T2-weighted spin-echo MR images of the right arm (repetition time msec/echo time msec, 2410/70) show a hyperintense soft-tissue mass (arrows) in the belly of the right biceps muscle preserving the muscle fibers (arrowheads) without disruption.
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Figure 1b: Oblique (a) sagittal and (b) coronal fat-saturated T2-weighted spin-echo MR images of the right arm (repetition time msec/echo time msec, 2410/70) show a hyperintense soft-tissue mass (arrows) in the belly of the right biceps muscle preserving the muscle fibers (arrowheads) without disruption.
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Figure 2: Transverse T2-weighted gradient-echo MR image of the right arm (488/14; flip angle, 35°) shows a moderately high–signal-intensity intramuscular soft-tissue mass (arrows). There are no important blood- or calcification-related signals.
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Figure 4: Contrast material–enhanced sagittal T1-weighted spin-echo MR image of the right arm (600/15) shows a soft-tissue mass (arrows) with almost homogeneous enhancement preserving the muscle fibers without disruption.
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DISCUSSION
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The keys to assigning the correct diagnosis were patient age, history of recent trauma, and a rapidly growing, painful solitary soft-tissue mass located in the substance of the biceps muscle, together with MR findings. The soft-tissue mass had well-defined margins with homogeneous signal intensity similar to that of muscle on T1-weighted images and almost homogeneous enhancement after intravenous injection of gadopentetate dimeglumine. On T2-weighted images, the lesion was hyperintense and preserved muscle fibers without discontinuation. The continuous muscle fibers were also distinctly seen on contrast-enhanced MR images. On gradient-echo images, no signal intensity changes related to blood or calcification were detected. These clinical and imaging findings were indicative of proliferative myositis (PM). Incisional biopsy was performed, and the pathologic examination findings enabled us to confirm this diagnosis.
PM is a rare benign inflammatory myopathy characterized by infiltration with basophilic giant cells and proliferative fibroblasts. Kern (1) described this disease in 1960. It occurs most commonly in adults (mean age, 50 years), although it has been described in children, and it usually arises in the head and neck region or in the upper extremities (2,3). Patients with PM present with a rapidly enlarging solitary soft-tissue mass that is often firm and painful (3). The mass may appear and double in size within a few days or weeks. The cause of PM is unknown, but a history of recent local trauma is noted in some cases (1–3).
PM may be classified as a subtype of pseudosarcomatous proliferative soft-tissue lesions. The other subtypes (proliferative fasciitis, nodular fasciitis, intravascular fasciitis, and cranial fasciitis) could not be considered in the differential diagnosis because of their locations. Among these, proliferative fasciitis typically involves the subcutaneous tissue but not the deep fascia, and it forms a poorly circumscribed lesion. Nodular fasciitis is most commonly located in the soft-tissue fascia deep to the skin but still superficial to the muscles, and it forms a well-circumscribed mass (4).
Imaging of soft-tissue masses typically begins with conventional radiography. Radiographs may reveal nonspecific well- or ill-defined soft-tissue masses with or without calcification. Soft-tissue masses of PM may rarely extend to adjacent osseous structures (5). Ultrasonography and computed tomographic (CT) findings are nonspecific. CT usually reveals a mass that is hypo- or isoattenuating relative to the skeletal muscle, and contrast enhancement may be homogeneous, heterogeneous, or absent (3). MR images of PM have been reported in several cases, with a hypo- or isointense T1 signal compared with that of muscle and homogeneous enhancement. T2-weighted MR images typically demonstrate a hyperintense soft-tissue mass (3,5,6).
Once the diagnosis has been established, the recommended follow-up strategy is no specific treatment, since PM may disappear spontaneously (3,6). Excision may be preferred to establish a diagnosis and for cosmetic reasons. Recurrence is extremely rare.
Differential considerations for a mass involving the skeletal muscle include soft-tissue tumors, traumatic injury, myositis ossificans, muscle sarcoidosis, and various causes of infectious and inflammatory processes.
The most common benign and malignant intramuscular soft-tissue tumors are angiomatous lesions, lipoma, myxoma, malignant fibrous histiocytoma, and various types of sarcomas (7). Soft-tissue angiomatous lesions and lipomas can be diagnosed confidently on the basis of their specific signal intensity and morphologic characteristics on MR images. Typically, T1-weighted MR images demonstrate soft-tissue masses of intermediate signal intensity with interspersed areas of high signal intensity, as well as almost homogeneous high-signal-intensity masses that correspond to fatty areas (8,9). Soft-tissue myxomas often display characteristic MR findings, including an intramuscular location, a surrounding rim of tissue similar to fat, and high water content resulting in signal intensity lower than that of skeletal muscle on T1-weighted MR images and markedly high signal intensity on T2-weighted MR images (10). These features made myxoma an unlikely diagnosis in this case. The aggressive course of the clinical presentation may suggest malignant fibrous histiocytoma and sarcomas in the differential diagnosis. However, the presence of a painful mass following trauma; well-defined lesion margins; lack of infiltration in the adjacent soft tissues; and, specifically, identification of the preserved muscle fibers inside the lesion on MR images made these diagnoses less likely.
Lymphoma could be considered, but skeletal muscle involvement in this entity is rare and usually reflects diffuse involvement of multiple muscle groups, affects multiple neighboring muscle compartments, and metastasizes into other soft tissues (11,12). Focal muscle involvement has been reported; however, it too is rare, and the morphologic soft-tissue findings enabled us to exclude this diagnosis.
Homogeneous contrast enhancement of the intramuscular lesion on MR images enabled us to easily exclude different categories of traumatic muscle injuries, although the lesion developed after trauma. Rhabdomyolysis is a distinct form of severe muscle injury. It may result from a variety of insults, including trauma, severe exercise, ischemia, burns, toxins, intravenous heparin therapy, and autoimmune inflammation. It is characterized by loss of integrity of muscle cell membranes (13,14). MR images reveal edema throughout the involved muscle, which may progress to myonecrosis. Rhabdomyolysis can also be ruled out by determining levels of muscle enzymes in the blood.
Myositis ossificans is another main cause of an intramuscular soft-tissue mass. It is not an inflammatory myopathy. There is usually a history of local trauma, but it may be seen in patients with paralysis, burns, tetanus, or an intramuscular hematoma. It may also develop spontaneously (15). Several MR appearances corresponding to the stages of maturation of myositis ossificans are noted (16,17). The area that may ossify peripherally within 6–8 weeks is swollen and painful during the 1st days or weeks of the acute phase, and it shows rim enhancement after contrast agent injection at this early stage (17). Although the clinical features and unenhanced MR imaging findings indicated a diagnosis of myositis ossificans, the enhancement pattern enabled us to rule this out as the most likely diagnosis.
Muscular sarcoidosis may manifest at MR imaging in the form of focal intramuscular masses, which are often seen at the musculotendinous junction. Involvement of the muscle may result in tenderness. These masses may be multiple and bilateral and more commonly involve the lower extremity (18,19). The lesions have an umbilicated appearance, with a bright rim and central low signal intensity on T2-weighted and contrast-enhanced images that create a "dark star" appearance (19). The clinical features and imaging findings of muscular sarcoidosis are not consistent with the findings in this case.
Muscle denervation, polymyositis, and dermatomyositis are well-known entities that can be ruled out with clinical and laboratory findings (20,21). Although the other various causes of muscle infections that cause edema without abscess or necrosis can be considered in the differential diagnosis, the clinical and laboratory findings in this case were also not consistent with infection.
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FOOTNOTES
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2 Current address: Department of Radiology, Trakya University School of Medicine, Edirne, Turkey.Authors stated no financial relationship to disclose. 
| Part one of this case appeared 4 months previously and may contain larger images.
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References
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- Kern WH. Proliferative myositis: a pseudosarcomatous reaction to injury. Arch Pathol 1960;69:209–216.[Medline]
- Enzinger FM, Dulcey F. Proliferative myositis: report of thirty-three cases. Cancer 1967;20:2213–2223.[CrossRef][Medline]
- Mulier S, Stas M, Delabie J, et al. Proliferative myositis in a child: a case report. Skeletal Radiol 1999;28:703–709.[CrossRef][Medline]
- Batsakis JG, el-Naggar AK. Pseudosarcomatous proliferative lesions of soft tissues. Ann Otol Rhinol Laryngol 1994;103:578–582.[Medline]
- Kent MS, Flieder DB, Port JL, Altorki NK. Proliferative myositis: a rare pseudosarcoma of the chest wall. Ann Thorac Surg 2002;73:1296–1298.[Abstract/Free Full Text]
- Wlachovska B, Abraham B, Deux JF, Sibony M, Marsault C, Le Breton C. Proliferative myositis in a patient with AIDS. Skeletal Radiol 2004;33:237–240.[CrossRef][Medline]
- Kransdorf MJ, Murphey MD. Radiologic evaluation of soft-tissue masses: a current perspective. AJR Am J Roentgenol 2000;175:575–587.[Free Full Text]
- Konez O, Burrows PE. Magnetic resonance of vascular anomalies. Magn Reson Imaging Clin N Am 2002;10:363–388.[CrossRef][Medline]
- Matsumoto K, Hukuda S, Ishizawa M, Chano T, Okabe H. MRI findings in intramuscular lipomas. Skeletal Radiol 1999;28:145–152.[CrossRef][Medline]
- Murphey MD, McRae GA, Fanburg-Smith JC, Temple HT, Levine AM, Aboulafia AJ. Imaging of soft-tissue myxoma with emphasis on CT and MR and comparison of radiologic and pathologic findings. Radiology 2002;225:215–224.[Abstract/Free Full Text]
- Lee VS, Martinez S, Coleman ER. Primary muscle lymphoma: clinical and imaging findings. Radiology 1997;203:237–244.[Abstract/Free Full Text]
- Travis WD, Banks PM, Reiman HM. Primary extranodal soft tissue lymphoma of the extremities. Am J Surg Pathol 1987;11:359–366.[CrossRef][Medline]
- Shintani S, Shiigai T. Repeat MRI in acute rhabdomyolysis: correlation with clinicopathological findings. J Comput Assist Tomogr 1993;17:786–791.[Medline]
- May DA, Disler DG, Jones EA, Balkissoon AA, Manaster BJ. Abnormal signal intensity in skeletal muscle at MR imaging: patterns, pearls, and pitfalls. RadioGraphics 2000;20(Spec Issue):S295–S315.[Abstract/Free Full Text]
- Resnick D, Niwayama G. Soft tissues. In: Resnick D, ed. Diagnosis of bone and joint disorders. 3rd ed. Philadelphia, Pa: Saunders, 1995; 4491–4622.
- De Smet AA, Norris MA, Fischer DR. Magnetic resonance imaging of myositis ossificans: analysis of seven cases. Skeletal Radiol 1992;21:503–507.[Medline]
- Shirkhoda A, Armin AR, Bis KG, Makris J, Irwin RB, Shetty AN. MR imaging of myositis ossificans: variable patterns at different stages. J Magn Reson Imaging 1995;5:287–292.[CrossRef][Medline]
- Otake S, Ishigaki T. Muscular sarcoidosis. Semin Musculoskelet Radiol 2001;5:167–170.[CrossRef][Medline]
- Otake S. Sarcoidosis involving skeletal muscle: imaging findings and relative value of imaging procedures. AJR Am J Roentgenol 1994;162:369–375.[Abstract/Free Full Text]
- Fleckenstein JL, Watumull D, Conner KE, et al. Denervated human skeletal muscle: MR imaging evaluation. Radiology 1993;187:213–218.[Abstract/Free Full Text]
- Resnick D. Dermatomyositis and polymyositis. In: Resnick D, ed. Diagnosis of bone and joint disorders. 3rd ed. Philadelphia, Pa: Saunders, 1995; 1218–1231.
Congratulations to the 10 individuals that submitted the most likely diagnosis (proliferative myositis) for Diagnosis Please, Case 118. The names and locations of the individuals, as submitted, are as follows:
Individual responses
- Hisashi Abe, MD, Montreal, Quebec, Canada
- Erhan Akpinar, Ankara, Turkey
- Alexandra Araújo, Lisbon, Portugal
- Marc G. De Baets, MD, Agra, Switzerland
- Virginia Fattal Jaef, MD, Rosario, Argentina
- Mario A. Laguna, MD, Milwaukee, Wis
- David M. Panicek, MD, New York, NY
- Matthew C. Rheinboldt, MD, Nashville, Tenn
- Roberto Queiroz dos Santos, MD, Rio de Janeiro, Brazil
- Baris Ismail Turkbey, MD, Ankara, Turkey
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S. Subramanian, R. Sharma, and M. Kemal Demir
Can MR Imaging Be Used To Reliably Differentiate Proliferative Myositis from Myositis Ossificans?
Radiology,
March 1, 2008;
246(3):
987 - 988.
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HISTORY
IMAGING FINDINGS
