Left knee pain A large mass with aggressive features is seen arising from the medial femoral condyle and distal tibial metaphysis which extends into the adjacent soft tissues. It measures approximately 8.0 x 6.7 x 10 cm in the greatest transaxial and craniocaudal dimensions. The mass is iso- to hypointense to skeletal muscle on T1WI and slightly hyperintense to skeletal muscle on fat saturated T2 sequences and scattered areas of signal heterogeneity. There is extension of the mass to the weightbearing surface of the medial femoral condyle with irregularity of the subchondral bone plate, possibly representing a pathologic fracture.There is soft tissue edema of the thigh, including the VMO. There is a large joint effusion with both discrete and ill-defined foci of low signal intensity scattered throughout, likely representing a combination of blood products, cartilaginous fragments, and synovitis; however, cannot exclude the possibility of intra-articular seeding of tumor. There is a small Baker's cyst with fluid extending along the popliteal tendon. There is slight displacement of the VMO by the mass; the mass does not appear to extend into the popliteal vessels. A few slightly prominent lymph nodes are noted within the popliteal fossa which are all less than 1 cm.Note that evaluation of the articular cartilage and menisci is degraded by motion artifact and the large field of view provided to completely image the mass. Within these limitations, full-thickness cartilage defects are noted along the medial patellar facet with delamination of the articular cartilage of the femoral trochlea.The ACL, PCL, and LCL are intact. The MCL courses proximally along the medial aspect of the mass but is not seen at its proximal attachment. The extensor mechanism is unremarkable.
Large soft tissue mass with aggressive features arising from the distal femur highly suspicious for primary malignancy such as osteosarcoma. Correlation with conventional radiographs and referral to orthopedic oncology is recommended.Note that at the time of the study, the patient was currently admitted at Jackson Park Hospital (773-947-7500) and transferred for the purposes of routine knee MRI at University of Chicago Medical Center. These findings were discussed with Dr. B. Najeeb (resident for Dr. Syed Ali, the primary attending caring for the patient at Jackson Park Hospital) via telephone at 4:25 pm on the date of the exam. Also note that the order for MRI was initially placed by ancillary services prior to the patient's admission by Dr. Edward Pillar (708-924-8000) who was also made aware of the findings. 