Figure 5. 46-year-old female with extraskeletal osteosarcoma of the right thigh.

Findings: (A) Coronal STIR thigh MR image demonstrates a 7.9 × 5.2 cm superficial soft tissue mass (blue arrows). The central portion of the mass demonstrates predominantly high T2 signal. There is surrounding reticular high T2 signal within the soft tissues consistent with edema. There is also intramuscular edema (green arrows).

(B) Axial post-contrast T1 subtraction image demonstrates a lobular superficial soft tissue mass which extends to the skin surface. There is predominantly peripheral enhancement of the lesion with central signal which appears isointense to muscle. The tumor exerts mass effect on the adjacent underlying musculature with apparent extension through the bordering fascia (yellow arrow). Note the inhomogeneous fat suppression anterior to the soft tissue mass (orange arrow).

Technique: MRI of the right thigh performed with contrast, 1.5 T, coronal STIR (TR 5378, TE 20), coronal T1 post contrast (TR 566, TE 20), 9.6 cc Gadavist contrast.

Technique: Axial CT of the thigh with contrast, 240 mAs, 140 kV, 2 mm slice thickness, 75mL of Isovue 370 contrast.