Anteroposterior x-ray of the patient’s right knee
Axial magnetic resonance imaging of the knee
Computed tomography of the patient’s knee
A woman, aged 41 years, presents with progressive pain in the right knee for the last 4 months. Images were obtained from x-ray, magnetic resonance imaging, and computed tomography.
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Giant cell tumors (GCTs) are benign but locally aggressive tumors that typically involve the epiphysis and adjacent metaphysis of long bones. The distal femur is the most common location (more than 50% of GCTs occur around the knee), followed by the proximal tibia, then the distal radius.
Unlike most bone tumors, giant cell tumors are more prevalent in women aged between 30 years and 50 years. Giant cell tumors typically present as a solitary tumor that may enlarge and erode through the subchondral bone, articular cartilage, and ligaments. However, expansion through the articular cartilage is rare.
Symptoms may include pain, decreased range of motion of the affected joint, and a palpable mass on exam. Pain is worse with weight bearing and up to 12% of patients with GCTs will present with pathologic fracture.
GCTs are classified into 3 grades: Grade-1 GCTs (4%) are considered inactive and are not locally aggressive; grade-2 GCTs (74%) are locally aggressive tumors that expand into and thin the cortices; and grade-3 GCTs (22%) are locally aggressive, expand through the cortices, and may have soft tissue involvement.
Radiographically, GCTs can appear malignant in nature with bony destruction and cortical breakthrough. Magnetic resonance imaging (MRI) is helpful in differentiating GCTs from bone tumors with which they are commonly confused, such as aneurysmal bone cysts, brown tumor of hyperparathyroidism, chondroblastoma, osteosarcoma, and metastatic disease. Typical MRI findings include low intensity on T1-weighted images, homogeneous in nature, and well-defined borders without surrounding bone and soft tissue edema. Computed tomography (CT) is generally ordered to aid in choosing the biopsy location and determine degree of cortical thinning. Absence of intralesional calcification is consistent with GCTs.
A biopsy is necessary to make a definitive diagnosis. Histology results show classic multinucleated giant cells distributed evenly throughout the lesion.
GCTs may cause metastases to the lungs or lymph nodes, or they may undergo malignant transformation. Metastases to the lungs and lymph nodes behave the same way as the benign primary tumor. In rare cases, GCTs transform to a malignant sarcoma; transformation is thought to be caused by prior radiation exposure.
Treatment is often dictated by the tumor grade. The goal of treatment is to remove all tumor cells while still trying to preserve the integrity of the involved joint. Curettage alone results in unacceptable recurrence rates of up to 34%. Adjunct therapies, including phenol, cement, and liquid nitrogen, are often used after curettage in an attempt to further decrease recurrence rates. With adjunct therapies, recurrence rates drop to 3%. Once the tumor is removed, the void in the bone may be filled with cement or bone graft for structural support. Grade-3 tumors may require en bloc excision with wide margins. This may result in the need for a large osteoarticular allograft, joint reconstruction procedure, or amputation, depending on the function of the limb after excision.
Patients should be followed closely after treatment with serial radiographs of the involved site and chest to rule out pulmonary involvement. Recurrence rates have been reported to be from 3% to 25%, and GCTs have been found to recur as many as 12 years after treatment.
Dagan Cloutier, MPAS, PA-C, practices in a multispeciality orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants (JOPA).
- Randall RL, Ward R, Hoang BH. Chapter 5. Musculoskeletal Oncology. In: Skinner HB, McMahon PJ, eds. Current Diagnosis & Treatment in Orthopedics. 5th ed. New York, N.Y.: McGraw-Hill Education; 2014.
- Lewis VO, Aboulafia AJ. Giant cell tumor of bone. Orthopaedic Knowledge Online Journal. 2007;5(5).