What Is Osteochondroma (Bone Cancer)? Symptoms, Risks, and Treatment

Osteochondroma is the most common benign bone tumor, developing from bone and cartilage. It usually appears in childhood and adolescence and grows near the ends of long bones. Although it is considered benign, some cases can transform into a malignant bone cancer called chondrosarcoma, so careful follow-up is required.

Prof. Dr. Yavuz Arıkan, who has worked in orthopedic oncology for many years, emphasizes that osteochondromas that are not followed correctly can progress to a sarcoma picture, and that early diagnosis is therefore vital.

What Is Osteochondroma?

Osteochondroma is a growth that develops from the outer surface of bone, is covered by a cartilage cap, and is considered the most common benign bone tumor. It usually appears in childhood and adolescence and is seen near the growth plates of long bones.

The most common sites are:

• Around the knee (femur – thigh bone and tibia – shinbone)
• Shoulder and upper arm bone (humerus)
• Hip and pelvis
• Leg bones

Osteochondromas often cause no pain and are noticed only as a hard mass. As they grow, they can press on nearby muscles, tendons, nerves, and vessels and cause symptoms. Osteochondromas near a joint can restrict motion.

According to Prof. Dr. Yavuz Arıkan, even though osteochondromas are considered benign, their biologic behavior should be watched carefully. Some osteochondromas can change cellular structure over time and become more aggressive tumors.

Is Osteochondroma Bone Cancer?

Osteochondroma is not bone cancer at the outset. Medically it is classified as a “benign bone tumor.” In a defined group of patients and under certain conditions, however, osteochondromas can transform into a malignant bone tumor called chondrosarcoma. Chondrosarcoma is a type of sarcoma, that is, a bone cancer.

This transformation is seen especially when:

• The osteochondroma continues to grow in adulthood
• Pain increases at night and does not ease with rest
• The mass hardens and changes shape
• MRI shows thickening of the cartilage cap
• Size increases rapidly

These findings indicate that the osteochondroma may no longer be only a benign prominence and may be entering a process of malignant change.

Such suspicious osteochondromas are evaluated with advanced imaging and biopsy. Prof. Dr. Yavuz Arıkan emphasizes that adult osteochondroma patients are at higher risk in this regard and must be followed by a specialist orthopedic oncologist.

Osteochondroma Symptoms

Most osteochondromas cause no symptoms at first. As they grow, the following complaints can appear:

• A hard, fixed mass on the bone
• Regional pain that increases with movement or is constant
• Limited joint motion
• Numbness or tingling from nerve compression
• Visible deformity

If pain increases at night, the mass grows rapidly, or sudden tenderness develops, this may be an early sign of sarcoma transformation.

Why Does Osteochondroma Form?

The cause cannot be tied to a single factor in every patient. In most cases the tumor appears when cartilage cells deviate from the normal growth plate during bone growth and multiply in an uncontrolled way toward the outside of the bone. Osteochondromas therefore develop most often in childhood and adolescence, when bones lengthen rapidly.

Normally, cartilage cells in the growth plate allow the bone to lengthen. In some people these cells multiply in the wrong direction and form a prominence extending from the bone surface. This structure later ossifies and becomes an osteochondroma.

Genetic Factors and Hereditary Predisposition

Some osteochondromas have a genetic origin. In multiple hereditary osteochondromatosis (MHE), also called hereditary multiple exostoses, many osteochondromas develop in various parts of the body. This disease is autosomal dominant; if one parent is a carrier, the chance of it appearing in a child is high.

In patients with MHE:

• The number of osteochondromas is high
• Tumors appear at a younger age
• Deformity and limb shortening are more common
• The risk of chondrosarcoma (bone cancer) is much higher than in people without MHE

The rate of malignant transformation of osteochondromas in these patients is reported as 5–25%. This is considerably higher than in people with a single osteochondroma.

Why Do Some Transform Into Cancer?

Osteochondroma cells can accumulate genetic mutations over time. In patients with MHE, disorders in the EXT1 and EXT2 genes lead to uncontrolled cell growth. These cellular changes set the stage for the osteochondroma to transform into a sarcoma type such as chondrosarcoma.

According to Prof. Dr. Yavuz Arıkan, osteochondromas that continue to grow in adulthood or cause pain may already be losing their benign character at the cellular level.

Trauma and Environmental Factors

Although osteochondromas mainly originate from the growth plate, in some cases osteochondroma-like prominences can develop after:

• Bone trauma in childhood
• Disorders of bone development
• Previous surgery

These are usually different from true osteochondromas and have a lower risk of malignant transformation.

How Is Osteochondroma Diagnosed?

Diagnosis is not made simply by seeing a mass. The aim is not only to answer “Is this an osteochondroma?” but also to clarify whether there is a risk of malignant transformation. The diagnostic process should therefore follow orthopedic oncology principles.

1. Clinical Examination

Patients usually present after noticing a hard, immobile mass on the bone. Examination assesses:

• Firmness of the mass
• Tenderness to pain
• Relationship to movement
• Signs of nerve or vessel compression

Night pain, rapid growth, or new tenderness is a warning for sarcoma.

2. X-ray

This is the first and most important step in diagnosis. On X-ray:

• A prominence extending outward from the bone
• A structure connected to the parent bone
• Typical bone density

is seen. This appearance is often diagnostic for osteochondroma.

3. Magnetic Resonance Imaging (MRI)

MRI shows the cartilage cap, the most critical component of osteochondroma. The thickness of this cap is the most important indicator of malignant transformation.

• Less than 1 cm → generally safe
• Greater than 2 cm → chondrosarcoma risk increases

MRI also assesses:

• Soft-tissue extension
• Relationship to vessels and muscle
• Edema and invasion

4. Computed Tomography (CT)

CT shows bone structure in detail. It is preferred especially for osteochondromas of the pelvis, hip, and spine.

5. Biopsy (If Needed)

If imaging is suspicious, biopsy is required. If biopsy is done with the wrong technique, cancer cells can spread.

Prof. Dr. Yavuz Arıkan therefore requires that biopsy be:

• Taken from a site compatible with the planned surgical incision
• Performed according to oncologic rules
• Planned in advance

Can Osteochondroma Become Malignant?

Yes. A small proportion of osteochondromas can transform over time into a malignant bone tumor called chondrosarcoma. Chondrosarcoma is a type of sarcoma and is classified as bone cancer.

In whom is the transformation risk higher?

• Patients over 30
• Those whose osteochondroma continues to grow
• Those with multiple hereditary osteochondromatosis (MHE)
• Those who develop pain and night symptoms
• Those with hardening and shape change of the mass

In people with a single osteochondroma the risk is around 1%, while in patients with MHE it can reach 5–25%.

Early signs of transformation to cancer:

• A previously painless mass becoming painful
• Bone pain that wakes the patient at night
• Rapid growth
• Increased cartilage thickness on MRI
• Edema and firmness around the mass

When these findings appear, the patient should be evaluated urgently at an orthopedic oncology center.

What happens if it is caught early?

If chondrosarcoma is caught at an early stage:

• Limb-salvage surgery is possible
• Amputation is usually not needed
• Survival rates are very high

Prof. Dr. Yavuz Arıkan emphasizes that the greatest problem with bone cancers is late diagnosis, and that this risk can largely be prevented in osteochondroma patients who are followed regularly.

Treatment

The main goal of osteochondroma treatment is to protect the patient from unnecessary surgery while catching the risk of malignant transformation (chondrosarcoma) early. The approach is therefore individualized for every osteochondroma patient.

Prof. Dr. Yavuz Arıkan regards osteochondromas as “benign but potentially risky” lesions and balances observation and surgery according to scientific criteria.

Observation

For painless, small, non-growing osteochondromas, the first approach is usually regular follow-up. This is not “leaving it alone.” Follow-up is a systematic process for watching the tumor’s biologic behavior.

What is monitored?

• Increase in size of the mass
• Development of pain or worsening of pain
• Tenderness over the mass
• Restriction of joint motion
• Thickening of the cartilage cap on MRI
• Spread into nearby soft tissues

Follow-up intervals:

Patient group	Frequency of checks
Children and adolescents	X-ray + clinical examination once a year
Adults, painless	MRI every 6–12 months
Suspicious lesion	MRI every 3–6 months and biopsy if needed

Osteochondromas that continue to grow in adulthood are high risk for sarcoma transformation and these patients are followed more closely.

Prof. Dr. Yavuz Arıkan emphasizes that leaving adult osteochondroma patients without follow-up is one of the most common reasons bone cancer is recognized late.

Surgery

An osteochondroma must be removed surgically in the following situations:

• Constant or increasing pain
• Night pain
• Compression of a nerve or vessel
• Rapid growth
• Deformity
• Suspicion of malignant transformation
• Increased cartilage thickness on MRI

These situations suggest that the osteochondroma may no longer be a simple benign mass and may be entering a chondrosarcoma or other sarcoma process.

How Is Osteochondroma Surgery Performed?

Surgery is not an ordinary “mass removal.” If it is not done according to oncologic principles, tumor cells can spread into the surroundings.

Osteochondroma surgery follows these principles:

• The tumor is removed in one piece together with its capsule
• Nearby healthy bone and soft tissue are preserved
• If the bone has weakened, it is strengthened with graft or an implant
• In suspicious cases, intraoperative pathology (frozen section) is used

The aim is not only to remove the mass but to protect the patient from bone cancer that could develop later.

After Surgery

After correctly performed osteochondroma surgery:

• The recurrence risk is very low
• The patient’s pain disappears
• The chance of malignant change is eliminated
• Return to normal life is achieved

Even after surgery, the patient is followed at intervals. New osteochondromas can develop in some people with a genetic predisposition.

Conclusion and Specialist Opinion

Osteochondromas often look harmless, but if neglected they have the potential to cause serious results. Many patients ignore these masses because they are painless for years; a small proportion of osteochondromas, however, can transform into chondrosarcoma, that is, bone cancer. If this transformation is not caught early, the patient may face limb loss or a life-threatening sarcoma.

Prof. Dr. Yavuz Arıkan’s clinical approach is to treat osteochondromas not as “harmless bone prominences” but as potentially risky lesions. In this way:

• Unnecessary operations are avoided
• Patients at risk are directed to surgery in time
• Malignant transformations are caught at an early stage

If you have an osteochondroma and:

• Your pain is increasing,
• The mass is growing,
• Pain that wakes you at night has started,
• You notice a change in shape,

you should go without delay to a center specialized in orthopedic oncology. Correct follow-up and timely surgery allow osteochondroma to be fully controlled before it turns into bone cancer.

Frequently Asked Questions