Case contributed by Baqar Hasan


A 25-year-old man who presented with history of pain in the left knee for 3 to 4 months with no prior history of trauma or infection

Patient Data

Age: 25 years
Gender: Male

Well circumscribed, expansile, sub articular, eccentric, solitary lytic lesion with a narrow zone of transition in the meta-epiphysis of proximal end of tibia. The lesion has characteristic soap bubble appearance with minimal marginal sclerosis. A cortical break is also seen of the anterior margin. Mild periosteal reaction along the lateral margin of the lesion is present. Overlying cortex appears thinned.


There is a fairly defined heterogeneously enhancing lesion in the proximal meta-diaphysis of the left tibia with predominant hypo-intense signals. The tibialis anterior muscle is displace laterally by the lesion. The lateral cortex overlying the lesion is not clearly demarcated. A heterogeneously hyperintense focus is seen projecting anteriorly, may represent the area of cortical break seen on lateral plain x-ray.

Case Discussion

Osteoclastoma, commonly known as giant cell tumor, probably arises from zone of intense osteoclastic activity. It comprises 4-9% of all primary bone tumors and 18-23% of benign bone tumors. Peak age of involvement is during the 3rd decade. It generally occurs after closure of epiphysis, which is a main differentiating point from aneurysmal bone cyst (ABC). It usually involves long bones, subarticular in location, eccentric with a soap bubble appearance. Periosteal reaction, narrow zone of transition, lack of soft tissue component involvement, narrow permeative zone and benign nature of the presentation allow the lesion to be differentiated from osteosarcoma. MRI plays an important role in the assessment of the lesion.

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