A possible cause of multiple intramuscular masses: Mazabraud’s syndrome (2007: 11b)
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- Martin, S., Rapariz, J.M., Osés, M.J. et al. Eur Radiol (2008) 18: 417. doi:10.1007/s00330-007-0653-7
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Mazabraud’s syndrome is the association of fibrous bone dysplasia and myxomas in soft tissues. We present a new case of this condition in a 52-year-old female patient who presented with pain in the epigastric region. As an incidental finding an abdominal CT showed multiple hypodense intramuscular masses in the upper third of her left thigh associated with a bone lesion in the left femur and left ischiopubic ramus. A plain X-ray showed bone damage in those two bones with a ground-glass pattern and gross trabeculation, consistent with fibrous bone dysplasia. The MRI showed multiple intramuscular masses hypointense in T1-weighted images and hyperintense in T2-weighted images with contrast peripheral enhancement after administering an intravenous contrast agent, with the exception of one of the masses, which showed central enhancement, suggesting multiple myxomas. Very few conditions exist that present as multiple intramuscular masses. The association of multiple intramuscular myxomas and fibrous bone dysplasia should raise suspicion of the presence of this syndrome, and allows for the follow-up of lesions, preventing unnecessary biopsies. The objective of this report is to describe a new case.
KeywordsMazabraud’s syndromeFibrous dysplasiaMyxomaSoft tissues, neoplasmsSoft tissues, MRI
The association of fibrous dysplasia and intramuscular myxomas was first described by Henschen in 1926  and re-emphasized by Mazabraud in 1967  in the French literature. Luna et al.  reviewed the literature in 2005 to find only 60 published cases worldwide, two of them from their own series. To the best of our knowledge no further cases have been published since then, and this condition has been considered rare . This association, however, may be more frequent than previously thought, given that it presents as an asymptomatic disease in most cases, as in ours, where the condition was found by chance .
A plain X-ray may show an increase in soft tissues and bone lesions, usually showing cortical thickening, gross trabeculation and ‘‘ground-glass’’ pattern, which should suggest a diagnosis of fibrous bone dysplasia.
CT shows myxomas as hypodense and homogeneous masses intramuscularly located. After administering intravenous contrast agent there may be peripheral enhacement or central enhancement of contrast. Bone lesions show a gross pattern, evidencing neither cortical destruction nor radiological signs of aggressiveness.
MRI images show multiple intramuscular masses, with a homogeneous hypointense signal in T1-weighted images and a homogeneous hyperintense signal in T2-weighted images, which might be connected with a lesion of a cystic nature. Nevertheless, there may be peripheral or central enhancement following intravenous contrast medium, indicating the solid nature of these lesions . Bone lesions show a low intensity signal in T1-weighted images, whereas the intensity signal in T2-weighted images is variable and depends on the fibrous component of lesions and the associated cystic or hemorrhagic changes .
Macroscopically, histopathological findings show a jelly-like mass, without hemorrhage or necrosis. Microscopic examination shows a mass with scarce cellularity and extensive cystic degeneration.
The presence of multiple intramuscular masses and bone damage may suggest a diagnosis of malignant disease, mainly metastases. It is important to be aware of the existence of the association of multiple intramuscular myxomas and fibrous bone dysplasia to prevent unnecessary surgical procedures.
The association of fibrous dysplasia and intramuscular myxomas was first described by Henschen in 1926  and re-emphasized by Mazabraud in 1967  in the French literature. The etiology of Mazabraud’s syndrome is unknown. Different mechanisms have been put forth to account for the association of fibrous bone dysplasia and intramuscular myxomas, including a shared histological origin , a tissue metabolism anomaly or a developmental error, possibly associated with a genetic predisposition [4, 5].
Intramuscular myxomas are rare mesenchymal benign neoplasms frequently located in cardiac muscle, although other locations may also exist, including subcutaneous cell tissue, aponeurotic tissue, bone, genitourinary system and skin. Although myxomas have been largely described in the pathology literature, their radiological description is limited to a few cases .
Radiologically, intramuscular myxomas are usually single lesions that present as a mass of soft tissues, typically homogeneous and with well-defined borders. MRI shows them as well-bordered masses with a hypointense signal in T1-weighted images and markedly hyperintense signal in T2-weighted images. A peripheral enhancement or a central enhancement may be seen after administering intravenous contrast, indicating the solid nature of these lesions. Myxomas may be multiple, in these cases frequently being associated with fibrous dysplasia .
Fibrous bone dysplasia is a developmental anomaly typically affecting adolescents and young adults, in which normal bone marrow is replaced by fibrous tissue. It may present a monostotic or polyostotic nature.
Its radiologic aspect varies depending on there being either a higher bone or fibrous component. Lesions with a higher bone component are denser and more sclerotic, whereas lesions with a higher fibrous component are usually more radiolucent, with a characterisctic ‘‘ground-glass’’ pattern. CT show them as a central lesion sparing the articular space. As the lesion grows it expands the medullar cavity, with an intact cortex, although it is thinned by the expansive component. On MRI, the lesions are hypointense in T1-weighted images and show a variable intensity signal in T2-weighted images, depending on their histologic composition [8, 9].
Pathologic fractures are the most frequent complication. Sarcomatous transformation is rare, but possible .
In our case, a differential diagnosis with multiple intramuscular masses should be considered. Very few cases exist in which multiple intramuscular masses are produced [1, 10]. Lipomas may appear as multiple masses, although their usual location is in subcutaneous tissue, with their location in muscle tissue being rare. The pathognomonic findings of neurofibromatosis are plexiform neurofibromas [13–15]. Neurofibromas may show a superficial location, but they deepen and affect adjacent muscles. Musculoskeletal anomalies prevail in the most frequent form, NF1, whereas systemic manifestations prevail in NF2. Skeletal manifestations in NF1 present as an increase in bone tissue, scoliosis, pseudoarthrosis and pathologic fracture radiologically different from fibrous bone dysplasia. Only exceptionally may bone and muscle be affected in metastases . Lesions generally show a poorly defined border. Non-osseous involvement may exist in multiple myeloma, but it is limited to skin and subcutaneous tissue. Melanoma may produce subcutaneous mestastases, with intramuscular involvememt being very rare. Mafucci’s syndrome consists of multiple enchondromatoses and soft tissue hemangiomas that may pose a differential diagnosis for Mazabraud’s syndrome. McCune-Albright syndrome consists of polyostotic fibrous bone dysplasia, endocrine disorders and milk coffee-colored (cafe-au-lait) skin spots, but does not include intramuscular masses. Intramuscular abscesses and intramuscular myonecrosis [16–18] producing processes may present with a diffuse muscle edema pattern with formation of pseudomasses, although lesions are poorly defined, and no associated bone involvement is observed.
An association of multiple intramuscular masses and fibrous bone dysplasia should immediately suggest a Mazabraud syndrome diagnosis, thereby preventing unnecessary biopsies, assuming that the bone lesion represents a fibrous dysplasia and suggesting the appropriate follow-up .
Given the small but actual potential for sarcomatous degeneration in fibrous dysplasia, the presence of multiple intramuscular myxomas and fibrous bone dysplasia may be assumed to represent Mazabraud’s syndrome. Appropriate clinical and radiological follow-up of lesions may prevent unnecessary surgery.