Weekly Case

Title : Case 607

Age / Sex : 39 / M


Chief complaint: Left buttock mass

What is your impression?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Seung Hyun Lee, National Health Insurance Service Ilsan Hospital



Discussion


Answer: Intramuscular myxoma  


 


Findings: Well-defined intramuscular soft tissue mass involving the left gluteus maximus muscle. The mass demonstrates intermediate signal intensity on T1WI, high signal intensity on T2WI with perilesional high signal intensity on fluid-sensitive sequence (T2FS), with peripheral and septal enhancement.


 


Differential Diagnosis:


 neurogenic tumor, myxofibrosarcoma, lymphangioma, ganglion cyst


 


Discussion:


Clinical features


- Myxoma is a benign mesenchymal neoplasm that is composed of bland undifferentiated stellate cells with thin collagen fibers within a myxoid stroma. Myxoma is most frequently diagnosed in patients 40–70 years of age, with a 57% female predilection. Intramuscular myxomas are typically solitary. When multiple myxomas are present, they are almost always associated with monostotic or polyostotic fibrous dysplasia, known as Mazabraud syndrome. Most musculoskeletal myxomas are intramuscular (82%) in location, occurring most often in the thigh (51%), upper arm (9%), calf (7%), and buttock (7%). Management options include observation (because of the benign behavior) or surgical excision, which is typically curative without recurrence.


 


Imaging features


- US demonstrates a well-defined hypoechoic to near-anechoic mass with some internal echoes and increased through-transmission.


- CT typically shows a well-defined homogeneous soft-tissue mass with attenuation higher than that of water and less than that of surrounding muscle.


- MRI: Myxomas demonstrate homogeneous low (81%–100%) to intermediate (0%–19%) signal intensity on T1-weighted MR images. At T2-weighted MR imaging, all myxomas demonstrate high signal intensity. In 65%–89% of cases, a thin rim of fat is noted most prominently at the superior and inferior poles of the lesion, representing atrophy of the adjacent muscle associated with the slowly growing mass. Perilesional high signal intensity may be noted with the use of fluid-sensitive sequences in 79%–100% of myxomas, a finding caused by leakage of the myxomatous tissue into the surrounding muscle. Myxomas usually demonstrate mild (76%) to moderate (24%) contrast enhancement in a diffuse pattern (57%) or a thick peripheral and septal enhancement pattern (43%).  


 


References:



  • Soft-tissue myxomatous lesions: review of salient imaging features with pathologic comparison. Radiographics 2014; 34:964-980.

  • Intramuscular myxoma: characteristic MR imaging features. AJR Am J Roentgenol 2002; 178:1255-1259.


 



Correct Answer
Total applicants 29 Correct answers 16
Name Institution
남태훈 국군서울지구병원, 전문의
한유비 공보의, 전문의
윤유성 삼성서울병원, 전문의
권환웅 전공의
김보람 전문의
최형인 국군의무학교, 전문의
안준형 공중보건의, 전공의
장성원 중앙보훈병원, 전공의
박준동 뿌리병원, 전문의
신재환 국군춘천병원, 전문의
이준영 전공의
김동수 전공의
김창현 전문의
노윤화 전공의
이지현 삼성서울병원, 전문의
김형민 전문의


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