Presentation
Knee pain and swelling.
Patient Data
Expansile lytic lesion of the patella with cortical thinning but no discrete cortical destruction. No periosteal reaction. Internal soft tissue heterogeneity but no definite extracortical extension. No joint effusion.
Large expansile lesion affecting the patella with cortical thinning. It extends to the subarticular surface posteriorly but not into the knee joint. There are numerous fluid-fluid levels, and at the anterior aspect there is a thick area of solid tissue enhancement, with enhancing septa also present. Adjacent soft tissue edema.
Quadriceps tendon, patellar ligament, MPFL and LPFL are normal in signal and variably insert/originate from areas of tumor, thinned cortex and residual normal patella.
Case Discussion
There are a number of lesions that have a fluid-fluid level, most commonly aneurysmal bone cyst and giant cell tumor (also rare osteosarcoma subtypes). The enhancing soft tissue component favors this to be a giant cell tumor.
Unfortunately, this patient has been lost to follow-up and the pathological diagnosis is not known.
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