31-year-old woman with right femur Ewing's R, with retroperitoneal metastasis. Pain in lower extremity. There is a mass within the anterior compartment musculature of the proximal right thigh, predominantly involving the vastus intermedius muscle deep to the vastus lateralis. It is approximately 5 x 3 cm in transverse dimension and approximately 10 cm in craniocaudal dimension, representing a decrease in size when compared with the prior study. The mass is isointense to skeletal muscle on T1-weighted images, heterogeneously hyperintense to skeletal muscle on T2-weighted images, and shows diffuse but slightly heterogeneous enhancement following intervenous administration of gadolinium. There is focal atrophy of the vastus medialis muscle immediately distal to the mass. The mass abuts the lateral cortex of the proximal femoral diaphysis. Although I see no frank destruction of the underlying cortex, there is abnormal signal intensity and enhancement of the medullary bone of the underlying femur likely representing neoplastic involvement that has also decreased in extent when compared with the prior study. Patchy intermediate signal intensity within the remaining femoral diaphyses bilaterally likely reflects reconverted red marrow. Enhancing inguinal lymph nodes have overall decreased in size.
Decrease in size of Ewing sarcoma.