Case report 557: Solitary intramuscular myxoma in a patient with polyostotic fibrous dysplasia

Monosotic fibrous dysplasia and solitary intramuscular myxoma of the head and neck: A unique presentation of Mazabraud's syndrome and a literature review

Mazabraud's syndrome (MS) is a rare disease that is a combination of fibrous dysplasia and intramuscular myxomas. MS is a benign lesion and there is little data on the disease due to its low incidence. In the present study, the case of a 38-year-old patient who presented with a soft-tissue mass involving the masseter and swelling at the mandibular body and mandibular ramus is reported. Since the mandible is an important aesthetic and functional organ in the oral and maxillofacial region, surgery was primarily aimed at resecting the tumor, with good safety margins, and reconstructing the resultant defect. The lesions were pathologically diagnosed as MS. The unique features of this case included the painless and monostotic fibrous dysplasia, the solitary intramuscular myxomas involving the jaw and the male gender of the patient. MS usually occurs in the lower extremities, with an unusual predilection for the right limb; however, it rarely occurs in the head and neck region. A retrospective analysis of the clinical features and management of MS was also performed in the present study, together with a literature review. From the literature, it was concluded that the incidence of MS is ~2.3-fold greater in female patients than in male patients, and that the age of onset of MS ranges between 17 and 82 years, with an average age of 46.25 years.

Magnetic resonance imaging of intramuscular myxoma with histological comparison and a review of the literature

OBJECTIVE

To evaluate the magnetic resonance (MR) features of intramuscular myxoma (IM) compared with its pathological findings.

DESIGN

Two radiologists retrospectively reviewed records and imaging studies of patients with histologically proven IM. Two radiologists also analyzed by consensus all the MR studies (pre- and post-contrast T1-weighted and T2-weighted sequences) and a pathologist reviewed the available histological material.

PATIENTS

Seventeen patients with 18 histologically proven IM were reviewed. Histological samples of 11 of these 18 tumors were available for pathological analysis.

RESULTS

There were 14 women and three men, with a mean age of 58.9 years. IM involved predominantly the thigh (n=10). MR imaging showed well-circumscribed intramuscular masses, hypointense on T1-weighted and hyperintense on T2-weighted images. Eleven masses were homogeneous and seven slightly heterogeneous due to fibrous septa. Enhanced MR imaging demonstrated three different patterns: peripheral enhancement (n=1), peripheral and patchy internal enhancement (n=7) or peripheral and linear internal enhancement (n=4). Intratumoral cysts were detected in four masses. MR imaging showed the presence of a pseudocapsule (n=12), fat around the lesion (n=16) and peritumoral edema (n=16). Histologically, all the tumors were hypocellular, hypovascular and myxoid. Peripheral areas of collagenous fibers formed a partial capsule and IM often merged into surrounding muscular fibers. More cellular tumors and those with scanty myxoid stroma tended to show a more prominent internal enhancement.

CONCLUSION

IM shows several recognizable MR features which suggest its diagnosis.

Intramuscular myxoma with fibrous dysplasia: a report of two cases with a review of the literature

Two cases are reported of a rare association of intramuscular myxoma with fibrous dysplasia in a 70 and 40 year old Japanese woman, respectively. One of them had a solitary intramuscular myxoma, and the other patient suffered from two intramuscular tumors that had been initially misdiagnosed as myxoid liposarcoma. Only 24 cases of this kind of association have been recorded in the literature. This association should be taken into consideration to avoid inappropriate treatment, when cases of myxoid soft tissue tumor with a bone lesion are encountered.

Case report 800: Skeletal fibrous dysplasia associated with intramuscular myxoma (Mazabraud's syndrome)

In summary, intramuscular myxoma associated with fibrous dysplasia of bone represents a benign disorder of uncertain etiology. Magnetic resonance imaging has proved to be a useful diagnostic tool in the evaluation of this benign disorder. In addition, MR is a valuable aid in the preoperative planning process.

Magnetic resonance imaging of myxoid containing tumors

Myxoid tissue forms part of many benign and malignant soft-tissue tumors. The advent of percutaneous needle biopsy has made it important to be aware of the diagnostic implications of biopsy samples containing myxoid tissue. To determine whether the magnetic resonance imaging (MRI) characteristics could help establish the diagnosis, we compared the MR images of 11 tumors containing myxoid tissue with the resected tumor tissue. In our small series of these rare tumors, the MRI characteristics allowed differentiation of intramuscular myxomas from malignant neoplasms containing myxoid tissue. Intramuscular myxomas meet the following conditions: (a) they are well circumscribed; (b) they arise within muscle; (c) T1-weighted images demonstrate uniform, decreased signal intensity; (d) T2-weighted images demonstrate uniform increased signal intensity; (e) contrast-enhanced images exhibit an inhomogeneous increase in signal intensity. If any of these conditions is not met, then a malignancy containing myxoid tissue should be suspected.