Answer: Myxofibrosarcoma
Findings:
Well defined oval shaped mass
Subcutaneous layer, abutting the peroneus fascia
T1: Intermediate SI
T2: Heterogeneous high SI
Perilesional edema along the fascia with enhancement
Contrast enhancement: Heterogeneously intense enhancement
Differential Diagnosis:
Synovial sarcoma
Unusual peripheral nerve sheath tumor
Diagnosis:
Myxofibrosarcoma
Discussion:
Malignant soft tissue tumor
Previously known as myxoid malignant fibrous histiocytoma
Typically presents in elderly (6th decade)
Male predilection
Patients often present with painless enlarging soft tissue mass in extremities
MRI
T1
Intermediate (to low) SI
Heterogeneity if hemorrhage, calcification, necrosis present
Prominent enhancement of solid components
Especially in tumor periphery due to central location of hemorrhage, necrosis and myxoid component
T2
Intermediate to high SI
Heterogeneity if hemorrhage, calcification, necrosis present
Frequently shows curvilinear extensions of high T2 signal along fascial plane that also enhance → “tails” represent fascial extension of tumor at histopathological examination
References:
1. Origin and classification of soft tissue tumors. In: Kransdorf MJ , Murphey MD. Imaging of soft tissue tumors. 2nd ed. Philadelphia, Pa: Lippincott Williams & Williams, 2006; 1–5
2. Kransdorf MJ . Malignant soft-tissue tumors in a large referral population: distribution of diagnoses by age, sex, and location. AJR Am J Roentgenol 1995;164:129–134
3. Jones BC , Sundaram M , Kransdorf MJ . Synovial sarcoma: MR imaging findings in 34 patients. AJR Am J Roentgenol 1993;161:827–830
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