Giant Cell Tumor (GCT): What It Is, Why It Happens, and How It's Treated
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
A giant cell tumor (GCT) is a rare, benign bone tumor that typically develops near joints, most often near the knee [4] [5]. Symptoms include worsening bone pain, swelling, a visible lump and limited joint movement [4]. It is usually treated with surgery (curettage) and a bone graft [4] [5]. GCTs have a high recurrence rate, often returning within 2 to 5 years [4].
What the research says
Giant cell tumors mostly affect the lower limb, and they behave similarly in the arm and the leg. According to PubMed, a meta-analysis of 30 studies with 2,672 participants (mean age about 33) found these tumors predominantly in the lower extremities, with no significant difference in aggressiveness between upper and lower limbs (Saputra et al., Journal of Bone Oncology, 2025 [1]).
Denosumab gives high clinical and imaging response, but did not change recurrence rates. A systematic review of 26 studies and 1,742 patients found high rates of clinical benefit and imaging response with denosumab, mostly mild adverse events, and no change in local recurrence compared with patients treated without it (Barreto et al., World Journal of Orthopedics, 2025 [2]).
Cancerous change after denosumab is rare. In a meta-analysis of 800 denosumab-treated patients, the pooled incidence of malignant transformation was 3% (95% CI 2 to 7%), mainly in a high-risk subgroup, so ongoing surveillance is recommended (Alshaygy et al., Journal of Bone Oncology, 2026 [3]).
Study details are from PubMed abstracts.
What Is a Giant Cell Tumor?
A giant cell tumor (GCT), also known as an osteoclastoma, is a rare type of noncancerous growth [4]. These tumors typically form at the very end of your long bones, right next to a joint [4] [5]. While they are classified as benign — meaning they are not cancer — they are considered aggressive because they can grow rapidly and destroy the healthy bone around them [5].
Giant cell tumors are quite rare, affecting only about 1.7 people out of every million [4]. However, among noncancerous bone tumors, they are relatively common, accounting for 15% to 21% of all cases [4]. They most frequently affect young adults between the ages of 20 and 40 [4] [5].
Term | Plain-Language Meaning |
Giant Cell Tumor | A rare, aggressive, but noncancerous growth in the bone. |
Osteoclastoma | Another medical name for a giant cell tumor. |
Benign | Noncancerous; does not spread like malignant cancer. |
Curettage | A surgical procedure to scrape a tumor out of the bone. |
Most giant cell tumors develop near the knee, specifically at the bottom of the thigh bone (femur) or the top of the shin bone (tibia) [4] [5]. Less frequently, they may appear in the wrist, shoulder, hip, or tailbone [4]. If a similar growth forms in the soft tissues around a joint instead of the bone itself, it is called a tenosynovial giant cell tumor [4].
What Are the Symptoms of a Giant Cell Tumor?
The most common sign of a giant cell tumor is pain. At first, the pain might feel like a dull ache or a mild injury, but it typically worsens and becomes more constant as the tumor grows and puts pressure on the bone and surrounding tissues [4] [5].
As the tumor expands, you may notice other physical changes around the affected joint. Because the tumor weakens the bone, it can sometimes lead to a pathologic fracture, where the bone breaks during normal, everyday activity [4] [5].
Symptom | What You May Notice |
Bone Pain | Persistent pain that gets worse with activity and over time. |
Swelling | A visible or felt lump near a joint, such as the knee or wrist. |
Limited Mobility | Difficulty moving the joint through its full range of motion. |
Joint Pain | Tenderness or sharp pain specifically when moving the joint. |
What Causes Giant Cell Tumors?
Medical researchers have not yet identified the exact cause of giant cell tumors. They have found certain gene changes, or mutations, in many people with the condition, but these are generally not inherited from parents [4] [5]. The development of a GCT is not linked to your lifestyle habits, diet, or environment [4] [5].
Risk Factors
While most cases occur without a clear reason, two specific conditions are linked to a higher risk:
How Is a Giant Cell Tumor Diagnosed?
If you have persistent bone pain or a new lump, a healthcare provider will use a combination of imaging and tissue testing to confirm if a giant cell tumor is present. The most critical step is a biopsy, where a small sample of the tumor is removed and examined under a microscope. A specialist called a pathologist looks for the large, multi-nucleated "giant cells" that give the condition its name [4] [5].
Imaging tests are also used to see the size of the tumor and how much bone damage has occurred:
How Is a Giant Cell Tumor Treated?
Because giant cell tumors are aggressive and can destroy bone, the primary treatment is almost always surgery [4] [5]. The goal is to remove the entire tumor while preserving as much of the joint's function as possible.
Surgical Options
Curettage: The surgeon carefully scrapes the tumor out of the bone. To reduce the chance of the tumor returning, they may use chemicals or extreme cold (cryosurgery) to kill any remaining cells [5].
Bone Grafting: After the tumor is removed, the empty space in the bone is filled with a bone graft (from a donor or another part of your body) or bone cement to restore strength [4] [5].
Reconstruction: For very large tumors, a whole segment of bone may need to be removed and replaced with a metal prosthesis or a large bone graft [4] [5].
Nonsurgical Alternatives
If a tumor is in a location where surgery is too risky, or if it has returned multiple times, other treatments may be used:
Denosumab (Xgeva®): A medication given by injection that can shrink the tumor and help the bone regrow [4] [5].
Embolization: A procedure that cuts off the blood supply to the tumor [4] [5], causing it to shrink.
Radiation Therapy: High-energy beams used to kill tumor cells, usually reserved for cases that cannot be treated with surgery [4] [5].
Recovery and Long-Term Outlook
Recovery from GCT treatment depends on the extent of the surgery. You may need to use crutches for several weeks [4] and participate in physical therapy to regain strength and movement in the joint.
While giant cell tumors are rarely fatal, they have a high recurrence rate [4]. This means they often grow back in the same spot, even after a successful surgery. Most recurrences happen within the first two to five years [4], which is why you will need regular follow-up appointments and imaging for many years [4] [5].
Aspect | What to Expect |
Recurrence | High chance of returning; most often within 2–5 years. |
Metastasis | In very rare cases (about 1–3%), the tumor can spread to the lungs. |
Malignancy | Only about 4% of these tumors ever become cancerous. |
Monitoring | Life-long follow-up appointments are often recommended. |
Conclusion: Early Detection Is Essential
A giant cell tumor is a serious bone condition that requires prompt medical attention. Although it is not cancer, its aggressive nature means it can cause permanent damage to your joints and bones if left untreated. The good news is that with modern surgical techniques and new medications, most people can successfully manage the condition and maintain their mobility. If you notice new, persistent bone pain or a lump near a joint, consult an orthopaedic specialist immediately.
Comfort & Reassurance: While hearing that you have a "tumor" is frightening, remember that giant cell tumors are noncancerous. With early diagnosis and treatment by a specialist, the vast majority of patients recover well and return to their normal activities.
When to Seek Immediate Care
If you experience a sudden break in a bone without a major injury, or if you have severe, worsening joint pain that prevents you from moving, see a doctor right away. These can be signs that a tumor has significantly weakened your bone.
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Frequently Asked Questions
Is a giant cell tumor cancer?
No. It is a benign (noncancerous) tumor. However, it is aggressive and can destroy healthy bone tissue if not treated.
Where do giant cell tumors usually grow?
Giant cell tumors most commonly grow at the ends of long bones, particularly around the knee (the bottom of the thigh bone or the top of the shin bone).
What is the main symptom of a GCT?
Persistent and worsening bone pain is the most common symptom. You may also notice swelling or a lump near a joint.
Who gets giant cell tumors?
Giant cell tumors are most common in young adults between the ages of 20 and 40. They affect men and women roughly equally.
How is a giant cell tumor treated?
Surgery is the standard treatment. The tumor is scraped out (curettage) and the hole is filled with a bone graft or bone cement.
Can a giant cell tumor spread to other parts of the body?
In very rare cases (about 1–3%), a benign giant cell tumor can spread to the lungs. This is usually not fatal but requires treatment.
Why do these tumors have a high recurrence rate?
Because they grow within the bone, it can be difficult to remove every single microscopic cell during surgery. Any remaining cells can cause the tumor to grow back.
What is Denosumab?
Denosumab is a targeted medication (monoclonal antibody) that can help shrink giant cell tumors and strengthen the bone, often used when surgery isn't an option.
How long does recovery take?
Recovery varies but often involves several weeks of limited activity and physical therapy to restore joint function.
Can a GCT cause a broken bone?
Yes. Because the tumor eats away at the healthy bone, it can make the bone so weak that it breaks during normal activities. This is called a pathologic fracture.
Are giant cell tumors hereditary?
No. They are generally not passed down from parents to children and are not linked to family history.
What is the difference between a GCT and a tenosynovial giant cell tumor?
A GCT grows inside the bone, while a tenosynovial giant cell tumor grows in the soft tissues (like the lining of a joint) around the bone.
Will I need follow-up appointments?
Yes. Because of the high risk of the tumor returning, you will likely need regular check-ups and X-rays for at least five years, and sometimes longer.
What is curettage?
Curettage is a surgical technique where a doctor uses a tool called a curette to scrape out the tumor tissue from inside the bone.
Is there any way to prevent giant cell tumors?
No. Since the cause is unknown, there are currently no known ways to prevent them. Early detection is the best way to ensure a good outcome.
Related Reading
References
Saputra RD, et al. Comparative analysis of aggressiveness in giant cell tumor of bone between upper and lower extremities: A systematic review and meta-analysis. J Bone Oncol. 2025;51:100663. PMID 40028631. https://doi.org/10.1016/j.jbo.2025.100663
Barreto BG, et al. Denosumab regimens in the treatment of giant cell tumor of bone: A systematic review with meta-analysis. World J Orthop. 2025;16(3):102520. PMID 40124723. https://doi.org/10.5312/wjo.v16.i3.102520
Alshaygy IS, et al. Incidence of malignant transformation in giant cell tumor of bone following denosumab therapy: a systematic review and meta-analysis. J Bone Oncol. 2026;59:100778. PMID 42382831. https://doi.org/10.1016/j.jbo.2026.100778
Cleveland Clinic. Giant Cell Tumor (GCT): Symptoms, Causes & Treatment. Cleveland Clinic. Last updated December 6, 2024. https://my.clevelandclinic.org/health/diseases/22404-giant-cell-tumors
American Academy of Orthopaedic Surgeons. Giant Cell Tumor of Bone. OrthoInfo. Accessed October 15, 2026. https://orthoinfo.aaos.org/en/diseases--conditions/giant-cell-tumor-of-bone/
National Cancer Institute. Giant cell tumor. NCI Dictionary of Cancer Terms. Accessed October 15, 2026. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/giant-cell-tumor
Medical Disclaimer
This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have about a medical condition. Never disregard professional medical advice or delay seeking care because of something you have read here. If you think you may have a medical emergency, call your doctor or emergency services immediately.
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