Giant cell tumour of the distal femur

A 60-year-old man presented with a three-week history of increasing right knee pain, which led to the inability to bear weight.

A 60-year-old man was admitted to the accident and emergency department with a three-week history of an increasing right knee pain, leading to the inability to bear weight. There had been no trauma to the knee. On examination of the knee, it was found that there was a grade 3 effusion, tenderness over the medial femoral condyle and a reduced range of movement. The radiographs showed the presence of a cystic lesion in the medial femoral condyle with a pathological fracture entering the intercondylar region (Fig. 1). There was no sclerotic margin to the cyst and the cortex of the femur was preserved. An MRI scan was performed, which showed the lesion to be inhomogeneous with a mainly low signal intensity on T1-weighted images (Fig. 2) and a high signal intensity on T2-weighted images (Fig. 3). An isotope bone scan was performed, which showed a single area of increased activity around the distal femur (Fig. 4). Biopsy of the lesion was performed producing a tissue typical of a giant cell tumour with abundant, uniformly distributed, multi-nucleated, osteoclast-like, giant cells. The treatment was done by means of a curettage and packing of the cavity with a methylacrylate bone cement.

True giant cell tumours (GCTs) are relatively common tumours of bone, representing 5% of primary bone tumours. Important differential diagnoses are the secondary giant cell tumours of hyperparathyroidism and those of Paget's disease. They typically occur in the patients aged 20–50 years, with slightly more number of females being affected than males. The precise origin of the tumour cells is not known. Although they are considered to be benign, they can be locally aggressive and lung metastases can occur occasionally (3%). The pathological fractures are apparent at the time of presentation in 10%–30%. Local recurrence following the treatment is relatively common (5%–15%). GCTs predominate in the long tubular bones (75%–90% of cases). Over half are located adjacent to the knee. The femur is the commonest location (30%), followed by the tibia (25%), radius (10%) and humerus (6%). The rare locations include the spine (7%), hand or foot bones (5%), pelvis (4%), or indeed any bone. In mature long bones, the radiographic appearance is characteristic: the lesion is solitary, typically eccentrically located in the epiphysis abutting, but not breeching, subchondral bone. A portion of the metaphysis may also be involved. They are purely lytic in appearance, sometimes with fine trabeculation. The lesion's margins may be well or poorly defined. There may be cortical thinning, expansion or erosion with an extension of the tumour into the adjacent soft-tissues. The periosteal reaction or new bone formation is rare. In the skeletally immature GCTs, which are rare in the presence of open growth plates (2%), purely metaphyseal lesions are present. Isotope bone scintigraphy may show an increased activity beyond the true limit of the lesion. On MRI, GCTs are typically dark on T1-weighted images and bright on T2-weighted images; the tumour gives inhomogeneous signal intensity and fluid levels may be present.