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Age / Sex : 67 / M
Chief complaint : Palpable mass for 3 weeks, right
buttock
What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case. (Please submit only one answer)
Courtesy : Won-Hee Jee, Seoul St. Mary’s Hospital, The Catholic University of Korea
Diagnosis: Intramuscular myxoma
Discussion
Findings: MR images show a well
circumscribed mass within right gluteus maximus muscle. Coronal T1-weighted MR
image demonstrates a homogeneous, hypointense mass with perilesional fat rind. Axial
T2-weighted MR image demonstrates a homogeneously hyperintense mass with peripheral
edema. Coronal fat-suppressed contrast-enhanced T1-weighted image shows
heterogeneous enhancement. Diffusion-weighted images reveal no impeded
diffusivity.
Differential Diagnosis: benign
peripheral nerve sheath tumor, ganglion, cyst, other myxoid neoplasms
Diagnosis: Intramuscular myxoma
Discussion:
Intramuscuar myxoma
is the most common benign myxoid neoplasm, consisting of abundant myxoid stroma
interspersed with benign spindle cells. Intramuscular myxoma is most frequently
diagnosed in patients 40–70 years of age. The most common presentation is a
slowly growing painless mass. Intramuscular myxomas are typically solitary.
When multiple myxomas are present, they are almost always associated with
fibrous dysplasia, known as Mazabraud syndrome. Most musculoskeletal myxomas
are intramuscular (82%) in location, occurring most often in the thigh, followed
by upper arm, calf, and buttock. On MRI, the lesions are well circumscribed
with smooth or slightly lobulated margins, homogeneously hypointense on
T1-weighted images, and extremely hyperintense on T2-weighted images. On contrast-enhanced
images, lesions show variable heterogeneous, sometimes avid, contrast enhancement
due to the presence of abundant vascularity within the myxoid matrix. The
presence of a perilesional rind of fat or perilesional edema has been described
to be highly suggestive of the diagnosis on MRI. Surgical excision with wide
margins is the treatment of choice for intramuscular myxomas, with recurrence
being rare.
References:
1. Kransdorf MJ, Murphey MD (2014) Imaging of soft tissue masses In:
Kransdorf MJ, Murphey MD. Imaging of soft tissue tumors. 3rd ed. Philadelphia,
Pa: Lippincott Williams & Williams
2. Petscavage-Thomas JM, Walker
EA, Logie CI, Clarke LE, Duryea DM, Murphey MD. Soft-tissue myxomatous lesions:
review of salient imaging features with pathologic comparison. Radiographics
2014;34:964-80
3. Baheti AD, Tirumani SH, Rosenthal MH, et al. Myxoid soft-tissue neoplasms: comprehensive update
of the taxonomy and MRI features. AJR Am J Roentgenol. 2015;204:374-85
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