Age / Sex : 19 / M

Chief complaint: palpable mass in left thigh

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Myxoid liposarcoma

Discussion

Findings:

1) Plain radiography

- Anteroposterior radiograph of left thigh shows a soft tissue mass without calcification..

2) MR

- Axial T1-weighted fast spin-echo MR image shows homogeneously low signal intensity within mass. Sagittal T2-weighted fast spin-echo MR image shows marked high signal intensity on T2-weighted MR image. Contrast-enhanced axial and coronal T1-weighted fast spin-echo MR images show intense, heterogeneous enhancement.

Differential Diagnosis:

myxoid liposarcoma / myxoid MFH / myxoma

Diagnosis: Myxoid liposarcoma

Discussion:

Myxoid liposarcoma is the second most common type of liposarcoma and represents 20%–50% of all liposarcomas. Myxoid liposarcomas account for 10% of all soft-tissue sarcomas. Previously, myxoid and round cell liposarcomas were considered distinct histologic subtypes. However, the WHO Classification of Soft Tissue Tumors has now combined these lesions as myxoid liposarcoma, representing a continuum of these two previous subtypes. Extremity myxoid liposarcomas are most frequently intermuscular lesions (70%–80% of cases), and an origin in muscle or subcutaneous location is less common. These lesions predominantly affect the lower extremity (75%–80% of cases), particularly the medial thigh and popliteal regions.

Radiographs of myxoid liposarcoma may appear normal or more frequently reveal a nonspecific soft-tissue mass. Calcification occurs much less frequently than with well-differentiated liposarcoma. Similarly, radiolucent fat is also seen much less often compared with well-differentiated liposarcoma, owing to the much smaller volume of adipose tissue (often <10%) in these lesions.

The high water content of the lesion is reflected as predominant low signal intensity on T1-weighted MR images, and marked high signal intensity on T2-weighted MR images.

Myxoid liposarcomas enhance with contrast material at MR imaging, a characteristic that easily distinguishes these lesions from a cystic mass.

References:

1. Bredella MA, Stoller DW, Johnston JO. Bone and soft-tissue tumors. In; Stoller DW. Magnetic resonance imaging in orthopaedics and sports medicine, 3^rd ed, Philadelphia; Lippincott Williams & Wilkins, 2007:2140-2143

2. Murphey MD, Arcara LK, Fanburg-Smith J. Imaging of musculoskeletal liposarcoma with radiologic-pathologic correlation. Radiographics 2005;25:1371-1395

3. Sung MS, Kang HS, Suh JS, et al. Myxoid liposarcoma: appearance at MR imaging with histologic correlation. Radiographics 2000;20:1007-1019