Musculoskeletal · Bone Tumors
The facts most likely to be tested
Giant cell tumor of bone typically presents as a lytic lesion located in the epiphysis of long bones in skeletally mature patients.
Radiographic imaging classically demonstrates a soap-bubble appearance due to the expansile nature of the tumor.
Histopathology reveals numerous multinucleated giant cells scattered within a background of mononuclear stromal cells.
The most common site of involvement is the distal femur or proximal tibia around the knee joint.
Patients frequently present with localized pain, swelling, and decreased range of motion at the affected joint.
Giant cell tumors are considered locally aggressive and have a significant risk of local recurrence after curettage.
Pulmonary metastasis is a rare but documented complication, necessitating routine chest imaging for surveillance.
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A 28-year-old female presents to the clinic complaining of persistent dull, aching pain in her right knee for the past three months. She reports no history of trauma, but notes a palpable mass and swelling around the joint. Physical examination reveals tenderness over the distal femur and mild limitation in knee flexion. Radiographs of the right knee show a well-defined, expansile lytic lesion involving the epiphysis of the distal femur with a soap-bubble appearance and no periosteal reaction.
What is the most likely diagnosis?
Giant cell tumor of bone
The patient's age, the classic epiphyseal location, and the characteristic soap-bubble appearance on X-ray are pathognomonic for a giant cell tumor.
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Etiology / Epidemiology
Occurs primarily in skeletally mature adults (ages 20–40) with closed epiphyses.
Clinical Manifestations
Presents as localized pain and swelling; soap bubble appearance on imaging.
Diagnosis
Biopsy is the gold standard; imaging shows lytic lesions involving the epiphysis.
Treatment
Intralesional curettage is the primary treatment; pulmonary metastasis is a rare risk.
Prognosis
High local recurrence rate (up to 50%); requires long-term serial radiographs.
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Epidemiology & Etiology
Giant cell tumor (GCT) is a locally aggressive neoplasm most common in the third decade of life. There is a slight female predilection. It is rarely seen before physeal closure.
Pertinent Anatomy
The tumor typically arises in the epiphysis of long bones. The distal femur and proximal tibia (around the knee) are the most common sites of involvement.
Pathophysiology
GCT is characterized by a proliferation of mononuclear stromal cells and osteoclast-like giant cells. These cells express high levels of RANKL, leading to excessive osteoclast activity and bone resorption. This process creates the classic lytic, expansile bone lesion.
Clinical Manifestations
Patients present with progressive joint pain, swelling, and decreased range of motion. Pathologic fracture is a common presenting symptom. Radiographs reveal an eccentric, soap bubble lytic lesion that extends to the subchondral bone.
Diagnosis
The gold standard for definitive diagnosis is open biopsy or core needle biopsy. Imaging via MRI is essential to evaluate soft tissue extension and intra-articular involvement. Histology confirms the presence of multinucleated giant cells.
Treatment
Intralesional curettage with high-speed burring is the standard of care. Adjuvants like liquid nitrogen or phenol are often used to reduce recurrence. For unresectable or recurrent cases, denosumab (a RANKL inhibitor) is the preferred medical therapy. Do not use denosumab in patients with open epiphyses.
Prognosis
Local recurrence is common, necessitating serial radiographs every 3–6 months for the first 2 years. While histologically benign, it can rarely undergo malignant transformation or metastasize to the lungs.
Differential Diagnosis
Osteosarcoma: usually involves the metaphysis and shows sunburst periosteal reaction
Aneurysmal Bone Cyst: fluid-fluid levels on MRI
Chondroblastoma: typically occurs in skeletally immature patients
Brown Tumor: associated with hyperparathyroidism
Osteomyelitis: systemic signs of infection and elevated inflammatory markers