Presentation
Pain of the distal femur with local swelling.
Patient Data
There is a well-circumscribed geographic and expansive lesion of the medial femoral epicondyle with a displaced fracture the distal femur, medially.
CT shows a large and eccentric geographic lesion of the medial femoral epicondyle of the distal femur. The transition zone is narrow without reactive sclerosis on the endosteal side with a displaced fracture of the distal femur on the internal side. There is not matrix mineralization or periosteal reaction.
Low signal lesion on T1-weighted images, and intermediate signal on T2-weighted images with fluid-fluid level if associated with a secondary aneurysmal bone cyst. Fluid-fluid level there are also in the STIR sequences. Medially there is an extension in the periosseous soft tissues.
Histological report
Spindle cell and pleomorphic sarcoma with a high degree of malignancy with focal areas of necrosis. Skin free of neoplastic infiltration.
Case Discussion
Giant cell tumors are considered benign, however, they do rarely metastasize to the lungs and can be multicentric. They have a high potential for local recurrence when treated solely with a curettage. Characteristically they affect the articular ends of bone and may be associated with aneurysmal bone cysts.
CT is useful for demonstrating the absence of mineralization and for showing internal trabeculations as well as a subtle periosteal reaction. Campanacci et al. classified GCTs into three types based on their biological behavior, radiographic appearance, and degree of bone destruction:
- type I are considered latent with small intraosseous lesions
- type II are active and radiographically larger, with intact periosteum
- type III is aggressive and extends throughout the periosteum and surrounding tissues
Sarcomatous degeneration of giant cell tumors (GCT) occurs rarely and most of them are GCT previously treated with radiotherapy. The sarcomatous degeneration always has as a result high-grade sarcomas, with a high tendency to hematogenous dissemination.