An enchondroma is a common, benign bone tumor that develops inside the bone. Classified as a non-cancerous lesion, it arises from cartilage tissue and will not spread to other parts of the body. Enchondromas are frequently discovered incidentally during imaging for an unrelated injury or condition. Understanding the nature of this tumor and its management is important for those who receive this diagnosis.
Defining Enchondromas
An enchondroma is a slow-growing, benign cartilaginous tumor that forms within the central part of the bone, known as the medullary cavity. These tumors are composed of mature hyaline cartilage, the same tissue found at joint ends. Tumor formation is thought to result from an error in endochondral ossification, the process by which cartilage is normally replaced by bone during skeletal development.
The most frequent sites for a solitary enchondroma are the small bones of the hands and feet, where they are the most common type of hand tumor. They can also appear in larger, long bones like the femur, humerus, and tibia. Most people develop only a single lesion, referred to as a solitary enchondroma.
The development of multiple enchondromas throughout the skeleton is a less common condition known as enchondromatosis. This distinction is significant because multiple lesions weaken the bone more substantially and are associated with a different long-term outlook. The multiple forms are often linked to specific syndromes.
Recognizing the Signs and Underlying Causes
Most solitary enchondromas do not produce noticeable symptoms and are discovered incidentally on X-rays taken for other reasons. When symptoms occur, they relate to the tumor’s size or location. A potential consequence is a pathological fracture, a break caused by the structural weakness of the tumor, often accompanied by sudden pain.
If the lesion is large and located in the small bones of the hands or feet, it may cause localized swelling, tenderness, or a visible deformity. Researchers have identified mutations in genes, such as \(IDH-1\) and \(IDH-2\), that are implicated in the development of these cartilaginous tumors.
Multiple enchondromas are often a manifestation of specific genetic conditions, namely Ollier’s disease or Maffucci syndrome. Ollier’s disease is characterized by numerous enchondromas, frequently distributed on one side of the body, which can lead to limb length differences and bone deformities. Maffucci syndrome is a rarer condition that combines multiple enchondromas with hemangiomas, which are benign tumors of blood vessels in the soft tissues.
The Diagnostic Process
The initial step in identifying an enchondroma involves conventional X-ray imaging, as the tumor has a characteristic appearance. On an X-ray, the lesion typically presents as a well-defined, lucent area within the bone, appearing darker than the surrounding healthy tissue. Calcification within the tumor often shows a distinctive pattern described as “rings and arcs” or “pop-corn stippling,” which suggests a cartilaginous origin.
If the lesion is in a long bone and shows concerning features, such as large size or bone destruction, the doctor may order advanced imaging. A computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan provides a detailed view of the tumor’s borders and its relationship to surrounding tissue. These advanced scans help rule out other diagnoses and assess fracture risk.
Distinguishing a benign enchondroma from a low-grade chondrosarcoma, a malignant cartilage tumor, is a key part of the diagnostic process. This distinction is challenging because the two lesions can appear very similar on imaging and microscopic examination. If malignancy is suspected, a biopsy may be performed to obtain a tissue sample for histopathological analysis, though this is not required for all lesions.
Management and Long-Term Outlook
The management approach depends on whether the enchondroma is causing symptoms and its risk of future problems. For a solitary, asymptomatic enchondroma, the standard practice is “watchful waiting” with periodic follow-up imaging, such as X-rays. This monitoring tracks the lesion for changes in size or appearance and helps ensure that malignant transformation is not occurring.
Surgical intervention is necessary if the enchondroma causes persistent pain, presents a high risk of pathological fracture, or is associated with a significant cosmetic deformity. The most common procedure is curettage, which involves scraping out the tumor tissue from the bone cavity. The resulting defect is often filled with a bone graft—from the patient (autograft), a donor (allograft), or a bone substitute—to stabilize the structure and promote healing.
The prognosis for people with a solitary enchondroma is generally excellent, with a low chance of the tumor recurring after successful curettage and grafting. The risk of a solitary lesion transforming into a malignant chondrosarcoma is extremely low, estimated at less than one percent. However, for individuals with multiple enchondromatosis, such as Ollier’s disease or Maffucci syndrome, the risk of malignant transformation is significantly higher, sometimes reaching 25 to 30 percent, necessitating rigorous long-term surveillance.