What is Enchondroma?

Your bones are not just regular connective tissues; they are special because they can turn minerals, particularly calcium hydroxyapatite, into part of their structure. This mineralization not only gives your bones strength and toughness but also allows them to act as the body’s main storage for calcium (99%), phosphate (85%), and significant amounts of sodium and magnesium.

Your bones are primarily made up of two components. The inorganic component consists of mineral deposits, while the organic component is composed of bone cells and proteins that help build the structure of the bones.

The different kinds of bone cells include:

– Osteoprogenitor cells: These are just like stem cells that live on the surface of your bones. They have the potential to mature into osteoblasts, the cells responsible for bone formation.

– Osteoblasts: These cells are responsible for creating, arranging, and hardening the proteins in the bones.

– Osteocytes: These are the most common cells in bones. They participate in essential body functions like maintaining a healthy balance of calcium and phosphate.

– Osteoclasts: These cells are crucial for bone health as they contribute to the natural breaking down and rebuilding of bones.

Part of your skeleton begins to form from specific regions in your body even before you’re born:

– The craniofacial skeleton, the bones of your face and head, originate from the cranial neural crest.

– The axial skeleton, which includes your spine and ribs, forms from the paraxial mesoderm.

– The appendicular skeleton, which comprises your arms and legs, grows from the lateral plate mesoderm.

Interestingly, some bones can have tumors, benign growths that are not typically harmful. There are certain types of these benign bone tumors—called enchondromas—that form inside the bone or on the bone’s surface.

Enchondromas are most common in the bones of the hands and feet, although they can sometimes be found in other bones like the femur and humerus (the long bones in your legs and arms). Of note, the bones in the hands are the most common site for these tumors. Enchondromas typically appear during childhood due to abnormal development of growth plate or cartilage cells and can persist into adulthood. Though these tumors might show unusual cell growth patterns, they remain benign for the most part.

However, it’s worth noting that, in very rare cases, these tumor cells can become malignant and transform into a type of cancer called chondrosarcoma. But in almost all cases, the cancer arising from enchondromas is usually low-grade and seldom spreads to other parts of the body.

What Causes Enchondroma?

Enchondromas, which are a type of bone growth caused by lingering growth plate cells, or chondrocytes, in the bone, are not fully understood. The reason why these cells continue to stick around is not known, and genetic mutations, while rare, could have a role. These mutations often happen sporadically or unexpectedly.

Two genes known as isocitrate dehydrogenase-1 (IDH1) and isocitrate dehydrogenase-2 (IDH2) have been linked to enchondromas. If these genes mutate, they produce an altered form of the enzyme isocitrate dehydrogenase. This enzyme typically helps convert one chemical, isocitrate, into another, α-ketoglutarate. However, the mutated enzyme results in the production of an abnormal chemical called D-2-hydroxyglutarate (D-2-HG) instead.

D-2-HG can interfere with other enzymes that rely on α-ketoglutarate, which leads to DNA changes and alterations in histones—proteins which help to package and organize DNA. These changes encourage the formation of cartilaginous tumors and stop the normal development of mesenchymal stem cells—cells that can become a variety of cell types—into bone cells.

Another gene, the parathyroid hormone 1 receptor (PTHR1) gene, has also been found to mutate in enchondromas. This gene helps to control the process of turning cartilage into bone. Beyond this, a pathway known as the Indian Hedgehog pathway has been found to be overactive in some enchondromas, but the Wnt/β-catenin pathway—another biochemical pathway—can tone down this activity. Therefore, manipulating the Wnt/β-catenin pathway could be a possible way to treat enchondromas.

Risk Factors and Frequency for Enchondroma

Enchondromas are the most common type of tumor developing within the bones, making up about 3% of all bone tumors and 13% of all non-cancerous bone growths. These tumors are usually found in the small bones of the hands and feet, but they can also occur in the thigh (femoral) and upper arm (humeral) bones.

When someone has multiple enchondromas, this is known as enchondromatosis. A specific type of enchondromatosis, called Ollier disease, has uneven distribution in the arm and leg bones. This bone disorder is quite rare, occurring in about 1 in every 100,000 people.

Maffucci syndrome is an even rarer condition that involves enchondromatosis along with multiple soft tissue growths called hemangiomas and lymphangiomas. Less than 200 cases have been reported. Although these enchondromas resemble solitary ones under the microscope, the cells in this syndrome appear more abnormal.

Both Ollier disease and Maffucci syndrome carry an increased risk of developing a type of bone cancer known as chondrosarcoma and other types of internal cancers.

Signs and Symptoms of Enchondroma

Enchondromas, which are a type of noncancerous bone tumor, can show up at any age. However, they typically become noticeable in people’s 20s or 30s. When multiple enchondromas are present, symptoms usually appear before the age of 10. Often, these tumors are discovered when they cause a painful fracture, swelling, or deformity. In fact, 40% to 60% of people first realize they have an enchondroma due to a fracture. Others find out about their enchondroma when it’s spotted on an X-ray taken for an unrelated reason.

Enchondromas are often found in the large bones of the fingers, especially on the side of the pinky finger. If they occur in the end of the fingers, they can cause nail deformities.

In people suspected of having enchondroma, a thorough examination of the hand and wrist is crucial. Doctors need to assess the movement of finger joints and test the function of the muscles that flex and extend the fingers. This is because enchondromas located at the end of the fingers can cause a muscle that bends the finger to pull away from its attachment.

Patients who might have multiple enchondromas need a complete evaluation of the skin, chest, and abdomen, as well as their nerve and muscle function. This is because these individuals have a higher risk for developing various other problems, including multiple blood vessel tumors and cancers of the ovary and brain.

Testing for Enchondroma

If your doctor suspects you have a hand enchondroma, which is a kind of benign bone tumor, they will begin by obtaining x-rays of your hand from different angles. These tumors can look different on x-rays depending on their location and the extent of their calcification, or hardening due to a build-up of calcium. Usually, enchondromas show up as clear, solitary defects in the long bones. If the tumor is located centrally, it might look like a well-circumscribed area of rarefaction, a medical term meaning ‘decrease in bone density’, most commonly in the shaft of the bone. Tumors located just below the tough, outer surface of the bone might appear in well-defined defects.

Small areas of calcification may be visible within the tumors. If these areas are more pronounced, the tumor might resemble a bone infarct or a blockage of blood supply to the bone. Bigger lesions could lead to endosteal scalloping, which is an inward erosion or scooping out along the bone, part of the cortex thinning and expanding. If the lesion is heavily calcified, it might look like a bone infarction or bone islands. An advanced tumor might be associated with cortex thinning or a breach, expanding of the tumor and involving the surrounding tissue.

A CT scan can help evaluate the mineral content of the matrix, or the substance within the cells, and the integrity of the cortex. An MRI can assist in identifying aggressive and destructive features. However, it’s not easy to differentiate enchondroma from chondrosarcoma, which is a cancerous bone tumor, using an MRI. Both these types of tumors tend to show similar patterns in the first evaluation. Trying to differentiate these tumors using enhanced MRI hasn’t been proven effective. However, the presence of peritumoral edema, or swelling around the tumor, could better differentiate these tumors. In fact, studies have shown that chondrosarcoma is more likely to have peritumoral edema than enchondroma.

However, just finding a lesion on a radiologic study doesn’t necessarily mean it’s an enchondroma. Confirmation requires examining the biopsied lesion through histopathology. Yet, differentiating between benign and malignant hyaline cartilage lesions is even more challenging. In some cases, the suspicion of enchondroma or early chondrosarcoma might be strong but the diagnosis might remain uncertain even after extensive tissue examination. Indicators of possible malignancy include large size, presence of a large unmineralized component, significant thinning of the nearby cortex, greater bone scan activity, destruction of the chondrite matrix because of an expanding non-mineralized component, rapidly enlarging, painful lesion, and soft tissue mass.

There are only 2 known biomarkers that can differentiate enchondroma from chondrosarcoma, which are periostin and α-methylacyl-CoA racemase (AMACR). Periostin, a protein related to connective tissue, is reportedly missing in enchondroma but present in chondrosarcoma. In contrast, AMACR, an enzyme involved in the metabolism of fats, is often expressed by enchondroma but rarely by chondrosarcoma. However, further research is needed to confirm the usefulness of these biomarkers in diagnosing enchondroma and chondrosarcoma.

Treatment Options for Enchondroma

When it comes to enchondroma, a type of noncancerous bone tumor, there isn’t a one-size-fits-all treatment plan. If the enchondroma doesn’t cause any symptoms, doctors often advise keeping an eye on it without immediate treatment. Regular x-ray check-ups aren’t typically needed for these symptom-free cases. If the enchondroma is causing symptoms, breaks the bone, or prevents a clear diagnosis, surgery could be the best option.

When it comes to surgery for symptomatic enchondromas, the method typically used is curettage with bone grafting, ‘curettage’ means scraping out the tumor and ‘bone grafting’ is filling the resulting hole with replacement bone. The substitute bone can come from another part of the patient’s body (autogenous), a different person (allogeneic), or it can be a man-made material (synthetic). It isn’t yet known how these different types of bone grafts affect recovery, whether the condition comes back, potential complications, or the chance of the tumor becoming cancerous.

During the surgery, the doctors need to take care to prevent the tumor from spreading. They typically put a tourniquet on the patient’s limb that’s being operated on to control blood flow. Some surgeries also use a range of techniques to kill any tumor cells left behind such as using chemicals (phenol), freezing (liquid nitrogen, cryotherapy), heat (polymethyl methacrylate, electrocautery). Currently, though, no one method is deemed better than the others. After removal of the tumor, some surgeons fills up the hole left behind with bone grafts or bone cement. However, some recent studies have shown that leaving the hole empty can lead to similar results while reducing surgery time and potential complications.

The idea of using metal implants to prevent fractures in the affected bone is a contentious issue. Doctors uses the Mirels criteria, which take into account the tumor’s location, related pain and the size and type of the enchondroma, to assess a patient’s risk of fracture. If the score is 8 or more, the risk is significant and a metal implant to reinforce the bone might be suggested. If the score is below 7, the risk is low and an approach of just monitoring the enchondroma might be recommended.

Looking back at 23 years’ worth of patient records for enchondroma treatment, one study found that more than 80% of the patients had a full range of movement after their biopsy, curettage and allograft placement. The enchondroma rarely came back unless the patient had a specific condition called Ollier’s disease or the enchondroma was particularly large. If the patient’s bone was fragile and prone to break before the surgery, there was a greater chance of having limb function issues after the operation.

There are various surgical techniques that doctors can use for enchondroma. One individual case involved successful removal of the tumor via a ‘key-hole surgery’ approach followed by bone grafting. Another series of cases involved using screws to stabilize the bone after enchondroma removal, which yielded positive results. A study that looked back at 10 years of patient data found that ‘key-hole’ or minimally invasive surgery lead to faster recovery and fewer complications than traditional open surgery. A relatively recent method of treating enchondromas, radiofrequency ablation, where doctors use heat to kill the tumor cells, has shown promise, particularly in tumors located in the pelvis.

There are several conditions that share similar symptoms with enchondromatous lesions:

Bone infarction, which can look the same on X-ray images.
Tuberculous dactylitis, a type of joint infection that causes bone pain even when there’s no fracture.
Low-grade chondrosarcoma, a slow-growing bone cancer that also causes pain without a fracture.
Other harmless growths such as giant cell reparative granuloma, giant cell tumors, and chondroblastoma.

To tell them apart from enchondromas, a doctor needs to do a thorough clinical examination, order the right lab tests and imaging studies, and if needed, take a sample of the lesion for microscopic examination.

What to expect with Enchondroma

A solitary enchondroma, which is a type of benign (non-cancerous) tumor in the bone, usually doesn’t get worse over time. After being treated with a procedure called curettage, where the tumor is scraped out, and bone grafting, where new bone is added, it’s rare for this type of tumor to come back. However, larger tumors or those found in long bones, like your arms and legs, may be more likely to come back.

Enchondromatosis, a condition where you have multiple enchondromas, not only increases the chance of these tumors coming back but also raises the possibility of them turning into cancer.

Possible Complications When Diagnosed with Enchondroma

Delaying treatment for enchondroma, a type of noncancerous bone tumor, could lead to various complications. These might include:

Growth of the tumor inside the bone marrow (intramedullary) and its spread to the dense surface layer of the bone (cortical bone), which could cause the bone to break.
Interference with normal bone growth in children.
Increase in hospitalization costs due to surgeries needed to treat bone fractures caused by the disease.
Prolonged inability to move a body part and longer recovery time, if the surgery for such bone fractures is delayed until the bone heals.
Stiffness, deformations of the joint, and shortening of the muscle tissue that makes it impossible to stretch (contractures), especially in hands, after surgeries.
A rare chance (<1%) that the disease might turn into a type of bone cancer (chondrosarcoma), following full bone growth.

Furthermore, the risk of the disease developing into cancer is higher in Ollier disease and Maffucci syndrome. These conditions may also lead to tumors in other parts of the body, including the brain.

To avoid these complications, it’s crucial to promptly consult an orthopedic specialist if one suspects they have this condition.

Preventing Enchondroma

There aren’t specific ways to prevent enchondroma because we don’t fully understand what causes it. Some potential causes of this bone condition might be random genetic changes, but we can’t say for sure because these genetic changes don’t seem to follow a predictable pattern passed from parents to children. However, doctors may advise patients to adopt healthy lifestyle habits to keep their bones strong. These can include:

Eating a balanced diet loaded with essential nutrients for bone health like calcium and vitamin D.
Regularly seeing a doctor, especially if the patient has a family history of bone diseases.
Avoiding behaviors that could harm the bones, like smoking and drinking alcohol.
Taking safety precautions during sports and recreational activities to prevent injuries.

It’s important for patients to go and see a doctor right away if they keep experiencing symptoms like persistent pain or discomfort in their bones or muscles.

Frequently asked questions

Enchondroma is a type of benign bone tumor that can form inside the bone or on the bone's surface. It is most commonly found in the bones of the hands and feet, but can also occur in other bones such as the femur and humerus. Enchondromas typically appear during childhood and are characterized by abnormal development of growth plate or cartilage cells. While these tumors can show unusual cell growth patterns, they are usually benign and rarely become malignant.

Enchondromas make up about 3% of all bone tumors and 13% of all non-cancerous bone growths.

Signs and symptoms of Enchondroma include: - Painful fracture: Enchondromas are often discovered when they cause a painful fracture in the affected bone. - Swelling: The presence of an enchondroma can lead to swelling in the affected area. - Deformity: Enchondromas can cause deformities in the bone or surrounding tissues. - Nail deformities: If enchondromas occur in the end of the fingers, they can cause nail deformities. - Fracture as the first realization: 40% to 60% of people first realize they have an enchondroma due to a fracture. - Incidental discovery on X-ray: Enchondromas may be discovered incidentally when an X-ray is taken for an unrelated reason. - Muscle dysfunction: Enchondromas located at the end of the fingers can cause a muscle that bends the finger to pull away from its attachment. - Higher risk for other problems: Patients with multiple enchondromas have a higher risk for developing various other problems, including multiple blood vessel tumors and cancers of the ovary and brain. It is important to note that these signs and symptoms may vary depending on the location and severity of the enchondroma. A thorough examination by a doctor is crucial for accurate diagnosis and appropriate treatment.

Enchondromas are caused by lingering growth plate cells, or chondrocytes, in the bone. The exact reason why these cells continue to stick around is not known, but genetic mutations, although rare, could play a role.

The doctor needs to rule out the following conditions when diagnosing Enchondroma: 1. Bone infarction 2. Tuberculous dactylitis 3. Low-grade chondrosarcoma 4. Giant cell reparative granuloma 5. Giant cell tumors 6. Chondroblastoma

The types of tests that are needed for Enchondroma include: - X-rays of the hand from different angles to obtain a clear view of the tumor and its location. - CT scan to evaluate the mineral content of the matrix and the integrity of the cortex. - MRI to identify aggressive and destructive features, although it may not be effective in differentiating between Enchondroma and chondrosarcoma. - Histopathology examination of the biopsied lesion to confirm the diagnosis. - Biomarker tests, such as periostin and α-methylacyl-CoA racemase (AMACR), to differentiate between Enchondroma and chondrosarcoma, although further research is needed to confirm their usefulness.

The treatment for enchondroma depends on whether or not it is causing symptoms. If the enchondroma is not causing any symptoms, doctors usually recommend monitoring it without immediate treatment. Regular x-ray check-ups are not typically necessary for these cases. However, if the enchondroma is causing symptoms, breaking the bone, or preventing a clear diagnosis, surgery may be the best option. The most common surgical method used for symptomatic enchondromas is curettage with bone grafting, where the tumor is scraped out and the resulting hole is filled with replacement bone. The substitute bone can come from the patient's own body, another person, or a synthetic material. Other techniques such as using chemicals, freezing, or heat may also be used to kill any remaining tumor cells. The use of metal implants to reinforce the bone is considered on a case-by-case basis, depending on the patient's risk of fracture. Overall, the choice of treatment depends on the specific circumstances of each individual case.

The side effects when treating Enchondroma can include: - Growth of the tumor inside the bone marrow and its spread to the dense surface layer of the bone, which could cause the bone to break. - Interference with normal bone growth in children. - Increase in hospitalization costs due to surgeries needed to treat bone fractures caused by the disease. - Prolonged inability to move a body part and longer recovery time if the surgery for bone fractures is delayed until the bone heals. - Stiffness, deformations of the joint, and shortening of the muscle tissue that makes it impossible to stretch, especially in hands, after surgeries. - A rare chance (<1%) that the disease might turn into a type of bone cancer (chondrosarcoma), following full bone growth. - Higher risk of the disease developing into cancer in Ollier disease and Maffucci syndrome, which may also lead to tumors in other parts of the body, including the brain.

The prognosis for a solitary enchondroma, which is a benign tumor in the bone, is generally good. After treatment with curettage and bone grafting, it is rare for this type of tumor to come back. However, larger tumors or those found in long bones may have a higher likelihood of recurrence. In the case of enchondromatosis, where multiple enchondromas are present, there is an increased risk of these tumors turning into cancer.

Orthopedic surgeon

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