Tumors originating in cartilage can be either non-cancerous or cancerous, with enchondromas and chondrosarcomas representing these two categories. An enchondroma is a benign tumor that develops within the center of a bone. In contrast, a chondrosarcoma is a malignant tumor, meaning its cells are cancerous and can spread. Although both arise from the same tissue, their biological behaviors, locations, and clinical management are distinctly different.
Core Characteristics and Symptoms
An enchondroma is frequently discovered by chance during X-rays for unrelated injuries, as it is often asymptomatic. These benign tumors are most often found in the small bones of the hands and feet and are diagnosed in people between the ages of 10 and 40. Pain is not a common feature unless the tumor weakens the bone enough to cause a pathologic fracture. In some cases, multiple enchondromas can lead to bone deformities, such as enlargements in the fingers.
Chondrosarcomas, in contrast, almost always present with symptoms, the most common being a deep, dull, aching pain that often worsens at night. These malignant tumors tend to occur in older adults and are more frequently located in the flat bones of the pelvis or the long bones of the upper leg and shoulder. A chondrosarcoma may grow aggressively, leading to a palpable soft tissue mass as it extends beyond the bone’s cortex.
The Diagnostic Process
Distinguishing a benign enchondroma from a low-grade chondrosarcoma can be challenging due to their similarities on imaging and microscopic examination. The process begins with assessing radiographic images. On an X-ray, a lesion larger than 5 cm, with ill-defined margins or a lobulated shape, is more suggestive of a chondrosarcoma, while enchondromas tend to be smaller and well-contained.
Magnetic Resonance Imaging (MRI) provides a more detailed view of the tumor and its relationship with surrounding tissues. Features that point towards malignancy on an MRI include endosteal scalloping, which is the erosion of the inner layer of the bone’s cortex. The presence of a soft tissue mass extending beyond the bone or significant bone marrow edema are also indicators of a chondrosarcoma. Nuclear medicine bone scans can also be used, as chondrosarcomas often show increased radiotracer uptake.
A biopsy, where a tissue sample is examined by a pathologist, is often the definitive step but is not always necessary. For larger tumors in the long bones or pelvis, or when imaging reveals aggressive features like cortical breaching, a biopsy is required. Even with a tissue sample, differentiating a benign lesion from a low-grade malignancy can be difficult, making the combination of clinical symptoms, imaging findings, and pathology reports necessary for an accurate diagnosis.
Treatment Approaches and Prognosis
For asymptomatic enchondromas, the standard approach is observation. This involves periodic follow-up with X-rays or other imaging to monitor the lesion for any changes in size or appearance. Surgery is reserved for enchondromas that cause persistent pain or have resulted in a pathologic fracture. In these cases, the procedure is a curettage, where the surgeon scrapes the tumor out of the bone cavity, which is then often filled with a bone graft.
Treatment for chondrosarcoma is more aggressive and centers on complete surgical removal. The primary goal is a wide surgical resection, removing the tumor along with a margin of healthy tissue to ensure no cancer cells are left behind. For low-grade chondrosarcomas, this is often curative. Low-grade chondrosarcomas are resistant to both chemotherapy and radiation therapy, making successful surgery the primary treatment.
The prognosis for these two conditions differs. For enchondromas, the outlook is excellent, and they do not typically recur after removal. The prognosis for chondrosarcoma is highly dependent on the tumor’s grade and location, as well as the success of the surgery. Patients with low-grade tumors that are completely removed have a good prognosis, with five-year survival rates often exceeding 80%, while higher-grade tumors have a more guarded outlook.
Malignant Transformation Risk
A benign enchondroma can become a cancerous chondrosarcoma, but the risk varies. For a person with a single, isolated enchondroma, the risk of this malignant transformation is low, estimated to be less than 5%. This risk increases substantially in individuals with rare genetic syndromes characterized by multiple enchondromas, known as Ollier’s disease and Maffucci syndrome.
Ollier’s disease is defined by multiple enchondromas, often with an asymmetric distribution in the body. Maffucci syndrome includes multiple enchondromas along with soft tissue vascular growths called hemangiomas. In patients with Ollier’s disease, the lifetime risk of transformation can be as high as 25% by age 40, and the risk is greater for those with Maffucci syndrome. The risk is also proportional to the number and size of the lesions, with tumors in the pelvis and long bones being more prone to transformation.
Clinicians and patients must be vigilant for warning signs that could indicate malignant change. The development of new or worsening pain at the site of a previously asymptomatic enchondroma is a primary warning sign. Other concerning signs include a noticeable swelling over the bone, or evidence on follow-up imaging that the lesion is growing rapidly or eroding the cortex. Any of these symptoms would prompt further investigation to rule out chondrosarcoma.