What Is Osteoblastoma?

Overview

Osteoblastoma is a rare and benign bone tumour that accounts for 1% of all primary bone tumours. It is characterised by the presence of osteoblasts, which are bone-forming cells. Most cases are diagnosed during early adulthood, between the ages of 10 and 30 years, with a predominance in people assigned male at birth (AMAB).¹ Osteoblastoma is diagnosed with various imaging techniques and treatment usually involves surgery. It is important to accurately diagnose osteoblastoma as soon as possible for early treatment and good outcome. 

Classification and types of osteoblastoma

Osteoblastoma is commonly found in the spine and the sacrum, the base of the spine. It can also arise in the jawbone (mandible) and long bones, usually in the lower extremities like the thigh bone (femur) and shin bone (tibia).²

Osteoblastoma can be classified into 2 subtypes: conventional osteoblastoma and aggressive osteoblastoma.¹ Aggressive osteoblastoma in the spine, also known as spinal osteoblastoma, often results in bone destruction and infiltration into other tissues such as muscle, nerves, and blood vessels.¹ Even after surgical removal of spinal osteoblastoma, the benign tumour tends to grow back, can transform into a cancerous tumour, and may even spread to other parts of the body (metastasis).¹

Symptoms of osteoblastoma

Osteoblastomas generally grow quite slowly and do not have a lot of associated symptoms. If a patient does present symptoms, they usually experience dull and localised pain. Nonetheless, symptoms vary depending on where the benign tumour is located.²

Patients who have osteoblastomas close to the surface, may have local swelling and feel pain when the benign tumour area is touched.²

Patients with spinal osteoblastoma may experience lower back pain that is persistent and dull. This can be accompanied by muscle stiffness that is more pronounced during the daytime.¹ Some patients suffer other complications such as abnormal curvature of the spine (scoliosis) due to the muscular spasms caused by the inflammatory effect around the tumour.³ Moreover, if a tumour invades the space between the vertebrae, it compresses the nerve roots and the spinal cord, potentially causing neurological symptoms such as numbness, tingling, and an abnormal sensation.¹ In some cases, this can be as extreme as paralysis of the legs (paraplegia) or even paralysis. Unfortunately, neurological problems are quite common and occur in approximately 40% to 60% of osteoblastoma patients.¹

Patients with osteoblastoma in the neck often have a limited range of motion and a noticeable painful slope in the neck. 

Diagnosis of osteoblastoma

In osteoblastoma patients with no symptoms, lesions are found by chance during imaging for other medical conditions. However, if patients present some of the symptoms previously mentioned, a specialist will recommend the following diagnostic techniques. 

Radiography

Radiography is a medical imaging technique that uses X-rays to create images of the internal structures of the body, especially the bones. It is a painless and quick diagnostic technique that can be used to diagnose osteoblastoma. However, due to the complex anatomy of the spine, radiographs do not always detect osteoblastoma lesions. A study showed that osteoblastoma cannot be detected properly on radiographs in half of the patients.⁴ 

Computed tomography (CT) scans 

A CT scan is a medical imaging technique that combines the use of a series of X-rays and a computer to create a detailed view of the internal structures, more detailed than just an X-ray. According to several studies, a CT scan is one of the most suitable techniques to diagnose osteoblastoma properly.¹ It provides information on the degree of bone destruction and whether the lesion has spread to the nerves or muscles. Moreover, since it allows for precise visualisation of the tumour location, it helps plan the surgery strategy for the removal of the tumour.¹ 

However, CT scans cannot differentiate between spinal osteoblastoma and osteosarcoma, a cancerous tumour of the bone. In these cases, a biopsy is necessary to confirm the diagnosis. 

Magnetic resonance imaging (MRI)

An MRI scan is a medical imaging technique that combines the use of a strong magnetic field, radio wave pulses, and a computer to create an image of the internal structures. An MRI scan is good for visualising the accumulation of fluid in the bone marrow or soft tissues, like muscle, that happens around a tumour. It is especially helpful in visualising if the spinal cord is compressed, which is important information when deciding treatment strategy. However, MRI scans are not as useful as CT scans in showing subtle changes like the development and hardening of bone tissue.¹ 

Positron emission tomography (PET) 

A PET scan is a medical imaging technique that uses a radioactive drug (tracer) to show the metabolic or biochemical function of the different tissues and organs. The tracer is usually injected into a hand or arm vein and will accumulate in the body areas with higher metabolic or biochemical activity, marking the location of the osteoblastoma. It is the most sensitive method for describing osteoblastoma lesions since it can provide accurate information, such as whether the tumour has metastasized, and allow for a detailed treatment plan. Thus, a combination of PET with CT scans is the most suitable method for osteoblastoma diagnosis.¹ 

Treatment of osteoblastoma

Osteoblastoma must be diagnosed as early as possible for a timely and effective treatment to relieve pain and avoid metastasis. 

Treatment depends on the tumour location and extent of invasion of the muscle or nerve tissue. 

The main therapeutic strategy is to surgically remove the tumour. Since osteoblastoma is quite rare and the spine has a complex anatomy, there is no exact surgical procedure defined. In addition, spinal osteoblastoma is close to vital structures and can quickly grow in size; as a result, patients receive aggressive surgery. This results in positive clinical outcomes and prevents local recurrence.¹ Some of the most common complications after surgery include wound infections and haemorrhage at the site of surgery.

Unfortunately, some lesions cannot be completely resected due to the tumour location, tumour size, or potential loss of function. In these cases, other possible treatments are radiation therapy, to reduce the tumour size or chemotherapy.¹

After receiving surgery, most osteoblastoma patients are cured. However, 10% to 20% of patients have a local recurrence of the tumour months or years after the surgery.²

Summary

Osteoblastoma is a non-cancerous bone tumour. It usually occurs in the spine or in the long bones of the lower extremities and it affects twice as many people AMAB than people assigned female at birth (AFAB). Many patients do not experience symptoms, but sometimes it can manifest as dull and localised pain. It is important to understand the symptoms associated with osteoblastoma to facilitate a timely diagnosis and effective treatment. Consult with a healthcare specialist for personalised information. 

FAQs

Is osteoblastoma cancerous?

No, osteoblastoma is a benign tumour. However, a study has shown that osteoblastoma can transform into a bone cancer type known as osteosarcoma.⁵ 

Can osteoblastoma be cured?

Yes, osteoblastoma can be removed by surgery, after which a patient is usually considered cured. 

Can osteoblastoma be prevented?

The exact cause of osteoblastoma is unknown, and there are no well-established risk factors. It can occur sporadically, and there is no strong evidence linking it to specific environmental or genetic factors.

What is the difference between osteoblastoma and osteoid osteoma?

Osteoblastoma and osteoid osteoma are both benign bone tumours that account for 14% and 12% of all benign bone tumours, respectively. Both conditions can develop at any age but usually affect people around the age of 20. It is between two to four times more frequently diagnosed in people AMAB.⁶ Osteoblastoma lesions measure 3 cm on average but can grow up to 15 cm in diameter, whereas osteoid osteomas are smaller in size and usually measure less than 1.5 cm in diameter. Importantly, osteoblastoma can be aggressive so experts recommend surgically removing the tumour, whereas osteoid osteoma is not as aggressive and usually the tumour goes away on its own within 6 to 15 years.⁶ 

What is the difference between osteoblastoma and osteosarcoma?

Osteoblastoma is a benign bone tumour, whereas osteosarcoma is a cancerous bone tumour. Osteosarcoma is quite rare but characterised by difficult treatment consisting of surgery combined with chemotherapy. The five-year survival rate for localised osteosarcoma is 77%, meaning 77 out of every 100 patients with local osteosarcoma are alive five years after being diagnosed. However, if the osteosarcoma has spread to other parts of the body, then the five-year survival rate falls below 25%.⁷