Different types of tumors can develop at the expense of bone tissue. In children and young subjects, the vast majority of benign tumors that are not life-threatening are encountered, such as osteochondromas (exostoses), frequently located in the knee. When these tumors are large and cause pain or functional impairment, they must be operated.

Definition

Bone tumors are tumor lesions caused by an abnormal proliferation of pathological cells located in the bone.

Bone tumors can be benign or malignant, that is, cancerous. Benign tumors are not life-threatening, but some can grow quickly and even be aggressive locally.

The different cell lines present in bone can be affected: bone tissue, cartilage, connective tissue, etc. Bone can also be the site of bone marrow tumors, which are linked to cancers of the blood and lymphomas (cancers of the lymphatic), not discussed here.

A distinction must be made between primary bone tumors, which originate in the bone, from secondary bone tumors, that is to say from metastases resulting from the migration of cancer cells from other tissues.

There is a wide variety of bone tumors, classified by specialists according to the type of cells that constitute them and their location.

Pseudo-tumors

Pseudotumors are lesions that present clinically and on imaging as tumors, although not consistent with abnormal cell proliferation. They tend to regress spontaneously over the years. These include non-ossifying fibroma, a very common benign pseudo-tumor lesion in children which disappears in adulthood, or essential bone cysts.

Primary benign tumors

Osteochondroma (or osteogenic exostosis) is formed by an outgrowth of misdirected growth cartilage. The tumor increases in size as it grows and often reveals itself in adulthood. It is preferentially located at the knee, but can also develop on flat bones, vertebrae or ribs. 

Osteoid osteoma is a tumor rich in bone cells called osteoblasts, richly vascularized. It is most often found on long bones (femur, tibia, etc.) but other locations are possible: vertebrae, spine, hands and feet, etc. 

There are also other types of benign bone tumors that are rarer, for example giant cell tumors, chondromas or osteoblastomas.

Primary malignant tumors

Osteosarcomas can affect different parts of the bone. They most often develop on the bones of the limbs, especially on the femur and tibia near the knee, but can also be found near the hip, at the pelvis, etc. Some are very aggressive and immediately present with metastases.

Ewing’s sarcomas involve large bones (pelvis, legs, etc.).

Chondrosarcomas develop from cartilage tissue.

Causes and risk factors

In most cases, there is no specific cause that can explain the development of a benign bone tumor. However, genetic factors and even physical or chemical influences seem to play a role in some cases. Certain tumors also develop in the context of a congenital syndrome such as the disease of multiple exostoses, known as Bessel-Hagen.

Primary bone cancers can in particular be favored by heredity, by hormonal disorders or bone pathology, by radiotherapy or even by pre-existing bone pathologies.

Diagnostic

The presence of a bone tumor may be suspected following palpation of an unusual mass, bone pain or the appearance of a pathological fracture. Sometimes its discovery is fortuitous.

The diagnosis should make it possible to rule out other types of bone lesions (infections, bone calluses formed by scar tissue) and to specify the nature of the tumor. It is guided by the patient’s age and history.

Various imaging exams are performed by specialists in the musculoskeletal system. An x-ray usually does not give enough information and a CT scan is the exam of choice. MRI is useful in some cases.

These examinations make it possible to specify the appearance, location and extension of the tumor. If these are sufficient to identify some benign tumors with a typical appearance, as a rule, a bone biopsy is necessary to clarify the diagnosis. The removal of a bone sample is performed either surgically or using a fine needle (trocar) with imaging guidance. 

The microscopic study of the tissues taken (anatomo-pathology) allows the diagnosis to be made.

Biology makes it possible to look for blood markers of inflammation or cancer.

The people concerned

Bone tissue is a major site of tumors secondary to another cancer: up to 75% of people with advanced breast or prostate cancer are at risk of developing bone metastases. Lung, kidney and thyroid cancers, as well as melanoma, also frequently lead to bone metastases. These metastases are generally observed in subjects over 50 years of age. 

Primary bone tumors are much rarer and only represent less than 1% of all primary tumors. They are most often found in children and young people.

In more than 90% of cases, these are benign tumors:

• About 35% of children aged 2 to 12 (three times out of four of boys) have a non-ossifying fibroid. 
• Osteochondroma represents about 20% of benign bone tumors. Rather, it affects adolescents and young adults. 
• Osteoid osteoma represents 10% of benign bone tumors. Four times out of five, it affects people under the age of 30, with a slight male predominance.
• Giant cell tumors (4 to 5% of primary bone tumors) mainly affect adults between the ages of 20 and 30.

There are also around 300 new cases of malignant primary bone tumors per year in France. In pediatric oncology, according to the French register, the number of new cases is estimated at 5,5 per million inhabitants under the age of 15.

• Osteosarcomas are the most common malignant bone tumors, but only affect between 100 and 150 patients per year, mainly males aged 10 to 20 years. 
• Ewing’s sarcoma is also rare (100 new patients per year in France). It is mainly seen in girls aged 5 to 9 and boys aged 10 to 14, but can also occur in adults under 30.
• Chondrosarcoma is the most common primary malignant bone tumor in adults (10 to 25% of cases). Predominantly male, it is very rare in children and mostly affects adults aged 30 to 60, the average age of onset being between 35 and 45 years.

Small bone tumors are usually asymptomatic. In other cases, they are manifested by pain of varying intensity, intermittent or permanent, which may be increased at night or on the contrary by daytime activity.

This pain may be directly related to the extension of the tumor or related to a complication such as cracking or fracture of the bone. They are then localized in the area of ​​the tumor.

Other times, the pain is related to irritation or compression of adjacent tissues, with varying consequences. A vertebral tumor can, for example, result in sciatica because it is accompanied by the compression of a nerve root, while the attack of a rib will cause respiratory problems. Other lesions will be manifested by motor or joint disorders, or even by edema.

Benign bone tumors only require treatment if they cause pain or other symptoms, or pose a risk of complications.

Surgery is the standard treatment. Surgical removal of the tumor or its curettage is performed, whether or not associated with filling the bone cavity (cement or bone graft). Internal fixation (reconstruction of the bone) may be necessary.

The treatment of primary malignant tumors and metastases is a matter of oncology and is discussed on a case-by-case basis. It may involve surgery, chemotherapy or radiotherapy.