Diagnostic challenge of clear cell chondrosarcoma at proximal tibia: A case report

Introduction: Clear cell chondrosarcoma (CCC) is a rare neoplasm originating from the epiphyseal cartilage. The ratio of males is higher, which peaks in the third and fourth decades. Common locations are the proximal femur and humerus, in this case in the proximal tibia. There is often misdiagnosis clinically and radiologically in CCC, generally diagnosed as a giant cell tumor (GCT) because it grows slowly and has the same location as GCT. Radiological findings suggest GCT, and MRI suggests an aggressive primary bone tumor. On a fine needle aspiration biopsy examination, the distribution of osteoclast-type multinucleated giant cells and atypical round oval cells was found, concluding that GCT cells were atypical. Confirmation of the diagnosis is required by histopathology and immunohistochemistry.
Case Presentation: Histopathology showed hyaline cartilage tissue containing atypical chondrocytes with proliferating large round cells, partially centrally located oval nuclei with clear cytoplasm, and suspected CCC. Furthermore, immunohistochemical examination showed positive S100 expression, so the diagnosis of CCC could be established.
Conclusion: Clear cell chondrosarcoma (CCC) is a rare but important bone tumor that can be easily misdiagnosed as a giant cell tumor (GCT) due to its similar clinical presentation and radiological features. Accurate diagnosis relies on a combination of histopathology and immunohistochemistry, particularly the identification of S100 expression. This case highlights the importance of considering CCC in the differential diagnosis of epiphyseal bone tumors, especially when conventional imaging findings suggest a benign tumor, to ensure proper management and treatment.