Age / Sex : 38 / M

Chief complaint: palpable mass in right thigh

What is your impression?

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

(답안은 한 개만 보내주시기 바랍니다)

Courtesy: 김현주 (Hyun Joo Kim), 순천향의대 서울병원(Soonchunhyang University Seoul Hospital)

myxoid liposarcoma

Discussion

Findings:

 CT.

There is about 15 x 8 x 3 cm sized lobulating contoured well defined mass in right rectus femoris muscle. The mass shows fat density with inner nodular portion. Also there is well enhancement in that nodular portion.

MRI

There is about 15 x 8 x 3 cm sized lobulating contoured well defined mass in right rectus femoris muscle with T1 and T2 heterogeneous high SI - slightly lower SI than subcutaneous fat.

Also there are T1 and T2 low SI nodular portions inside of the mass and fat suppression of predominant adipose component after fat saturation.

The nodular portions show well enhancement.

There is a fluid signal intensity (T1 low and T2 bright high SI) portion in inferior aspect of the mass with enhancement.

There is no definite perilesional infiltration and no inguinal enlarged lymph nodes.

Differential Diagnosis:

Well differentiated liposarcoma.

Extraskeletal myxoid chondrosarcoma

Diagnosis:  

Myxoid liposarcoma

Discussion:

 Myxoid liposarcoma

•       General consideration

–      2^nd m/c type of liposarcoma (20-50% of all liposarcoma)

–      No sex predilection

–      Younger than other type liposarcoma

•       4^th-5^th  decades

–      Location

•       Predominantly affect lower extremity (75-80%)

–      Medial thigh, popliteal lesion

•       Intermuscular lesion

–      Clinical appearance

•       Painless soft tissue mass

•       Quite large at presentation (>15cm)

•       Pathologic feature

–      Well-circumscribed, multinodular masses

–      Varies  depending on the degree of myxoid and round cell components

•       High-water content myxoid tissue and prominent cellular region of round cell

–      Sparse mature adipose tissue

–      Generally low to intermediate grade lesions.

•       High grade, if substantial round cell component (>5%)

–      Scant  mitoses

–      Reciprocal translocation of  t(12;16)(q13;p11)

•       Imaging features

v  Typically large, well-defined, and multilobulated intermuscular lesions.

v  CT

v  Attenuation lower than adjacent muscle (not isoattenuated to pure fluid)

v  Variable enhancing pattern depending on cellularity, vascularity

v  Small volume of fat density seen in septa or as subtle small nodules

v  MR

v  T1 low SI and T2 marked high SI due to myxoid component

v  Fatty septa or small adipose nodules in a myxoid mass

v  Enhance with contrast material: Peripheral nodular(61%), central nodular(44%), diffuse(17%)

v  Prominent round cell component

v  Lower fluid contents -> Similar attenuation with muscle on CT

                                                 Intermediate SI on T1 and T2 WI

v  Metastasis : Extrapulmonary soft tissue sites.

                           -> retroperitoneum, paraspinal region, bone

•       Differential diagnosis

–      Other soft tissue tumor with myxoid component

•       Extraskeletal myxoid chondrosarcoma, intramuscular myxoma

References:

1.     Imaging of Musculoskeletal Liposarcoma with Radiologic-Pathologic Correlation.  RadioGraphics 2005; 25:1371–1395

2.     Imaging of Liposarcoma: Classification, Patterns of Tumor Recurrence, and Response to Treatment. Am J Roentgenol 2011; 197:W37–W43

3.     Myxoid Liposarcoma: Appearance at MR Imaging with Histologic Correlation RadioGraphics 2000; 20:1007–1019