OSTEOCHONDROMA: SYMPTOMS, CAUSES, HISTOLOGY, TREATMENTS - MEDICINE - 2025

The osteochondroma is a type of tumor that occurs in growing bones. The nature of this injury is benign and involves the bone surfaces that are still covered with cartilage. It then constitutes a prominence of bone and cartilage tissue also called exostoses.

In a long bone, two parts are recognized, the diaphysis or body and the epiphysis or end. When the bone is developing or growing, it presents an area –the physis- formed by cartilage, which is responsible for bone growth.

Lucien Monfils, from Wikimedia Commons

The physis is located in an intermediate area between the shaft and the ends, called the metaphysis. It is in this area where osteochondromas occur.

The cause of osteochondroma is not clear, although there is an outgrowth of the growth plate from the metaphysis. This cartilage is stimulated and grows parallel to the original bone. On the other hand, its origin is considered as a neoplastic predisposition.

This type of tumor can be single - solitary osteochondroma - but it can also be multiple. The latter originates as a consequence of genetic factors.

Although osteochondroma can be asymptomatic, the symptoms that are observed - pain, functional limitation - are as a result of the compressive effect of the tumor on the adjacent tissues.

It is the most common of benign bone tumors and 10% of all bone tumors. It occurs in the growing bone, so its appearance is usually before the third decade of life. The bones most affected are usually those of the upper and lower extremities.

When it is asymptomatic, the diagnosis is due to an occasional finding. When symptoms appear, the physical and radiological examination will reveal their existence.

The treatment of osteochondroma is surgical, consisting of the complete removal of the tumor.

Symptoms

There are two types of osteochondromas: those that correspond to single lesions or solitary osteochondromas, and those that include multiple lesions. In both cases, the symptoms due to tumor growth are similar, however, in the case of multiple tumors, other signs and symptoms are associated.

Most osteochondromas are asymptomatic, and for this reason they go unnoticed. They are usually hardened tumors found in the bone of origin, and they do not cause damage or alterations. When, due to their growth, they press on an adjacent tissue - muscle, tendon, nerve or even blood vessels - they produce symptoms.

Pain

Pain is the most common symptom of this type of mass. If tumor growth is significant enough, it can cause compression of the soft tissues, causing inflammation and pain. Pressure on a peripheral nerve will cause neuropathic pain.

Functional limitation

Both pain and tumor extension can cause relative functional limitation in the individual. The growth of an osteochondroma can even affect an adjacent joint by limiting its range of motion.

Paresthesia

Compression of a nerve produces a series of symptoms - paresthesias - that include tingling, itching, shocks and even pain. If the pressure is significant and prolonged, it can cause irreversible neurological damage.

Obstruction of circulation

It is usually rare, and occurs as a result of pressure on a blood vessel. If it is an artery, the interruption of circulation can cause damage to the tissues that it supplies (ischemia).

On the other hand, venous compression leads to the accumulation of blood from the venous return, called venous stasis.

Localized swelling or edema

It depends on the size of the tumor, as well as the involvement of the adjacent soft tissues. A large tumor may be visible and palpable on the body surface.

Symptoms associated with multiple osteochondromas

In addition to the symptoms that single lesions produce by compressive effect, osteochondromatosis presents characteristic signs and symptoms. The clinical presentation in this case depends on the presence of multiple lesions and their predominance in long bones.

- Bone deformity

- Abnormally short bones and, for this reason, shortening of the limbs.

- Moderate to severe functional limitation, secondary to the deformity.

- Trunk disproportionate to the length of the limbs.

Finally, acute and rapidly evolving symptoms associated with tumor growth after 30 years of age are suggestive of malignancy. The possibility of the transition from osteochondroma to osteosarcoma is very low.

Some experts claim that it is the product of a benign tumor being malignant, while for others it is a sarcoma that is misdiagnosed early on.

Complications

Although osteochondromas are benign and predominantly asymptomatic tumors, there are risks of presenting complications during their evolution.

- Permanent neurological damage due to prolonged compression of a peripheral nerve.

- Major vascular lesions, including aneurysms and pseudoaneurysms in the aretrial wall. This is due to the continuous rubbing, friction or compression on the blood vessels.

- Fractures of the tumor pedicle, leaving the tumor free acting as a foreign body.

- Malignancy. It has been described that 1% of osteochondromas can become malignant, becoming low-grade sarcomas. This risk is higher in cases of osteochondromatosis.

Causes

There are two types of osteochondroma, the single or solitary one and osteochondromatosis or multiple osteochondromas. The mechanisms that originate both types are under study, however, from the hypotheses currently raised, mechanisms that explain the causes of this tumor are postulated.

Solitary osteochondroma

Physiopathologically, an osteochondroma consists of a proliferation of cartilaginous cells -hamartoma- originating in the proximity of the metaphyseal growth plate. Later its development occurs moving away from this metaphysis.

Tumor growth responds to stimuli similar to those of bone development, consisting of hormones and growth factors. For this reason, tumor growth stops when bone growth stimuli cease, after the second decade of life.

The precise cause of osteochondroma is not very clear. It is currently accepted that the growth plate presents a fissure or exit from its location, promoting abnormal formation. Some factors that could contribute to the origin of the osteochondroma have been identified, including trauma or an abnormal perichondral ring.

The perichondral ring is a structure formed by epiphyseal fibers and the union of collagen fibers of the periosteum and perichondrium. Its function is to provide stability and mechanical support to the metaphysis, including the growth plate. A defect in this band can produce herniation of the growth plate and, therefore, an osteochondroma.

Trauma to the bone that affects the metaphyseal region also causes cartilage to leak or herniation, promoting tumor formation.

Osteochondromatosis

Multiple osteochondroma - osteochondromatosis - is a variety whose main cause is genetic. There is an autosomal dominant type of inheritance, the result of a mutation in the EXT genes.

Chromosomes 8, 11 and 19 have the specific sites where the EXT genes 1, 2 and 3 are found, related to this condition.

Those affected by osteochondromatosis will have the predisposition to develop multiple osteochondromas in the course of their life. These tumors will appear predominantly in the lower limbs.

Histology

Sarahkayb, from Wikimedia Commons

Biopsy constitutes one of the most accurate diagnostic methods so far. It is based on the histopathological -microscopic- study of a tissue sample to determine its abnormal characteristics.

The histology of osteochondroma has little difference from an osteocartilaginous sample of normal bone. In fact, it has a cartilage cover where the only different feature is being less organized. The size of said cover does not exceed 10 mm in width.

The cartilage of this type of tumor does not differ from the original growth plate, where extended cartilage cells are observed, arranged in rows, whose nuclei are usually round or oval, as well as single or double. The characteristics of the normal physis - reproduction, growth, hypertrophy, calcification and ossification - are present.

Bony characteristics are the same as those of cortical and trabecular bone, where the trabeculae have nuclei of calcified cartilage in their center. The underlying trabeculae formed by endochondral ossification of the covering contain central nuclei of calcified cartilage.

Osteochondroma consists of a proliferation or hamartoma of the bone metaphysis, where the growth plate is located. Both the periosteum - superficial layer - as well as the cortex and the medulla of the tumor are a continuation of the bone. Endochondral ossification below the periosteum indicates abnormal growth of the exostosis.

In addition to the cartilage tissue, there are covering tissue and even a synovial membrane, in contact with the covering cartilage.

Finally, the exostosis appears flat and attached to the bone - sessile osteochondroma - or with a small stem or pedicle devoid of cartilage.

Treatments

First of all, it should be considered that osteochondroma is a benign tumor, the growth of which ceases in adulthood. Even, most of the time, it is asymptomatic. However, factors such as the presence of symptoms, complications or the minimal probability of malignancy make its removal necessary.

The use of analgesics and anti-inflammatories is indicated to improve the symptom, especially when pain is present.

The treatment of choice in the case of ostechondroma is complete surgical resection. The objective of this surgery is to avoid possible complications present in the soft tissues and joint adjacent to the tumor, in addition to improving symptoms. Also, when tumors are superficial, they must be removed for cosmetic reasons.

In the case of osteochondromatosis, it is possible to consider surgery to avoid or correct the complications inherent to bone deformity or growth retardation. The diagnosis of osteosarcoma requires its excision as soon as possible.

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