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Table 1 Differences and similarities between GCT, CB, and ABC of the patella

From: Chondroblastoma of the patella with secondary aneurysmal bone cyst, an easily misdiagnosed bone tumor:a case report with literature review

Incidence rate 33% 16% 5%
Age (years) 20–40 15–20 10–20
Common location The distal femur, proximal tibia, and distal radius Proximal epiphysis of the femur, humerus, and tibia Epiphysis of the femur and tibia
Clinical presentation Knee pain Knee pain Knee pain
Physical examination Tenderness Tenderness Tenderness
Imaging findings X: osteolytic lesion, soap bubble appearance, non-sclerotic margin, and radiolucent lesion; CT: osteolytic lesion;
MRI: osteolytic lesion, hypointensity on T1WI, and hyperintensity on T2WI
X: osteolytic lesion with well-defined sclerotic margin, lobulated rims, and thinned cortex;
CT: osteolytic lesion with septation, sclerotic margins, and some intralesional calcifications;
MRI: lobulated lesion, iso/hypointensity on T1WI, and mixed intensity or hyperintensity focus on T2WI
X: geographic osteolysis, smooth borders, thinned cortices, and intact articular surface;
CT: fluid-filled multiseptate cavities without intralesional calcifications;
MRI: lobulated lesion with a fluid-filled cyst, hypointensity on T1WI, and hyperintensity on T2WI
Histone H3.3 mutation H3F3A H3F3B
With secondary ABC Yes Yes
Pathology Numerous giant cells, short spindle-shaped cells, bone tissue calcification, and a few mitotic figures Proliferating chondroblast with chondroid matrix, some multinucleated giant cells, “coffee bean” nucleus Necrosis and hemorrhagic cystic cavities or red cells
Treatment Intralesional curettage (benign GCT) or patellectomy with adjuvant treatment (aggressive GCT) Intralesional curettage followed by bone grafting Intralesional curettage followed by bone grafting