Chondrosarcoma is a malignant tumor composed of cartilage-producing cells. It is the second most common primary malignancy of bone, and one of the most difficult bone tumors to diagnose and treat. There are several types of chondrosarcomas.
Chondrosarcomas can be subdivided in several ways: by histologic grade, whether they arise de novo (primary) or from benign lesions (secondary), by location within the bone (central or peripheral), or by syndrome.
Division of chondrosarcoma lesions by histologic grade carries the most prognostic significance. The grade of the tumor is extremely important in terms of overall and disease-free survival. There is a significant difference in 10-year survival rates between patients with low-grade lesions and patients with high-grade lesions.1, 2
Histologic grading of chondrosarcomas can pose a diagnostic challenge to both the musculoskeletal pathologist and the surgeon. The histologic spectrum ranges from a benign cartilage lesion (enchondroma) to the high-grade or dedifferentiated chondrosarcoma.
Malignant lesions are often divided into three histologic grades: low (grade 1), medium (grade 2), and high (grade 3). However, although most pathologists agree with this three-tiered grading system, there is some variation in the grouping of lesions. This is exemplified by the fact that there are different percentages of grade 1, 2 and 3 tumors among the large chondrosarcoma treatment centers.3, 4, 5, 6
One of the main diagnostic dilemmas with chondrosarcoma is differentiating between benign active and low-grade malignant lesions. Histologically, these lesions can look very similar; thus, clinical and radiographic data must be used to distinguish between them.
Cartilage lesions can often be identified on the basis of their radiographic appearance. Enchondromas (benign cartilage lesions) are typically located in the metaphyseal and diaphyseal portions of the long bones and the short tubular bones of the hand. They are described as containing dense, stippled, or popcorn calcifications. There is no periosteal reaction, cortical breakthrough, or associated extra-osseous mass.
Chondrosarcomas have a more aggressive radiographic appearance. The specific radiographic findings depend on the type and grade of the lesion. A primary central chondrosarcoma generally arises within the metaphyseal portion of the bone. Low-grade chondrosarcomas often show endosteal scalloping and a small degree of osteolysis. Intermediate and high-grade lesions demonstrate more aggressive radiographic features, such as osteolysis, medullary expansion, cortical thickening, cortical disruption, and the presence of a soft-tissue mass.
Rosenthal and associates7 summarized the radiographic and computed tomographic findings in low-grade and high-grade lesions. Low-grade features include dense, widespread, and uniformly distributed calcifications and, when present, an eccentric lobular growth of a soft-tissue mass. High-grade features include faint amorphous calcifications, large noncalcified areas, and concentric growth of a soft-tissue mass.
Additional imaging modalities are often helpful in the diagnosis and staging of malignant cartilage lesions. Computed tomography (CT) can evaluate the osseous architecture for endosteal scalloping, cortical thickening, or disruption. In addition, CT is helpful in identifying the pattern and extent of calcifications.
Magnetic resonance imaging (MRI) is useful in determining the intraosseous extent of the lesion, particularly the nonmineralized portion of the lesion. It has been proposed that the percentage of medullary cavity that is occupied by the lesion is predictive of malignancy. Medullary fill greater than 90% is associated with the diagnosis of chondrosarcoma.8 MRI will also define the soft-tissue mass and its relationship to the surrounding anatomy, such as the neurovascular bundle, the joint, and the joint capsule.
All cartilage lesions, both benign and malignant, tend to be "hot" on whole-body technetium-99m diphosphonate bone scans. However, it has been postulated that chondrosarcomas, unlike enchondromas, tend to have greater uptake within the lesion compared with an internal standard such as the anterior superior iliac spine.9
The clinical presentation of cartilage lesions varies depending on the location and type of the lesion.
Benign cartilage lesions, enchondromas, of the long bones are usually asymptomatic and are most often incidental findings on radiographs. Rarely are these lesions painful. Generally, patients have pain—not from the lesion itself but from the surrounding soft tissues. This is especially common in enchondroma of the proximal humerus, in which the cause of the pain is not the lesion but rotator cuff dysfunction. Enchondromas involving the short tubular bones of the hand are often associated with pathologic fracture. They are most commonly seen in women in the fourth to eighth decades of life.
Malignant cartilage lesions, chondrosarcomas, are most common in men in the sixth to eighth decade of life. These lesions are generally located in the metaphyses of long bones. The most common locations are the pelvis, proximal femur, ribs, humerus, tibia, and scapula.
Patients with malignant chondrosarcomas typically present with a history of progressive pain. The pain is constant, not relieved with rest, and often interferes with sleep. Specific symptoms are related to the location of the lesion.
Patients with pelvic or proximal femur lesions may often present with knee or hip pain. However, pelvic lesions can remain asymptomatic until they are quite large, and can often present with only bowel and bladder symptoms.
Upper- and lower-extremity lesions can cause pain, weakness, and disability of the limb. Range of motion of the adjacent joint may be limited, and atrophy of the limb may be present.
Blood work and other laboratory tests are normal.
The role of biopsy in the diagnosis of chondrosarcoma is controversial. Biopsy is often performed only to confirm what is clinically and radiographically obvious. Biopsy of asymptomatic lesions or radiographic enchondromas is not recommended.
Biopsy of chondrosarcoma may be performed open or closed. Closed or core-needle biopsy is an excellent option when confirmation of a radiographic and clinical chondrosarcoma is desired. This is performed with the help of real-time imaging, such as fluoroscopy or CT.
Biopsies should be taken from the areas of most concern (ie, from the uncalcified matrix or area of osteolysis). However, the drawback of needle biopsy in the diagnosis of chondrosarcoma is one of sampling error. Chondrosarcomas are extremely heterogeneous, and high-grade lesions often contain areas of low- and intermediate-grade cartilage material. Thus, a needle biopsy may not localize the area of highest grade and should not be relied upon for definitive diagnosis of the grade of the lesion.
Some oncologists advocate an open biopsy when the diagnosis is not clinically evident to minimize the potential for sampling error. The decision to biopsy should be made by an experienced orthopaedic oncologist who takes into account the patient history, physical examination, and radiographic studies.
Primary chondrosarcomas arise de novo, whereas secondary chondrosarcomas arise within preexisting lesions, either from an enchondroma or from an exostotic chondrosarcoma. Less than 1% of solitary enchondromas and osteochondromas dedifferentiate into chondrosarcomas.
Osteochondromas, whether they are sessile or pedunculated, result from an outgrowth of the physis. They can be singular or multifocal, and are covered with a cartilage cap (less than 1 cm). During the normal growth of the patient, the osteochondromas enlarge via enchondral ossification; however, once the patient reaches skeletal maturity, the growth of the osteochondroma and its cartilage cap should cease. When secondary chondrosarcomas develop, exostotic growth resumes and the cartilage cap thickens.
Patients with secondary chondrosarcomas that arise from solitary exostoses have a better prognosis than patients with other chondrosarcomas. In general, these chondrosarcomas are low-grade, slow-growing lesions that have low metastatic potential. Thus, although there is a small risk of the lesion developing into a dedifferentiated chondrosarcoma, an enlarging osteocartilaginous exostosis should be resected because these lesions can obtain enormous size and cause local morbidity.
Only patients with hereditary multiple osteocartilaginous exostosis or with multiple enchondromas (Ollier's disease or Mafucci's syndrome) have a definable risk for developing a secondary chondrosarcoma. These patients should be followed closely. It has been found that 25% of patients with Ollier's disease will develop a secondary chondrosarcoma by the age of 40 years; 100% of patients with Mafucci's syndrome will develop a secondary malignancy (chondrosarcoma or carcinoma) sometime in their life.10
The treatment of conventional chondrosarcoma is surgical. The response of chondrosarcomas to chemotherapy and radiation therapy is limited. Radiation may be of benefit for local control of microscopic disease or for palliation. Chemotherapy may be of benefit in mesenchymal and dedifferentiated chondrosarcomas, but its effectiveness in conventional chondrosarcoma is low.
Wide/negative margins are the goal of surgical resection; local recurrence is associated with the type of margin obtained. Intralesional or debulking procedures have been found to result in recurrence rates as high as 93%.11, 12 Use of wide margins significantly improves local control and, therefore, long-term outcome.
The prognosis of patients with conventional chondrosarcoma depends on the grade and location of the lesion.
Patients with a pelvic chondrosarcoma have a poorer prognosis than patients with chondrosarcoma in an extremity. Bjornsson and associates6 showed that pelvic chondrosarcomas have a higher rate of local recurrence than do stage-matched chondrosarcomas of the long bones.6 This tendency may result from the difficulty in obtaining adequate margins because of the close proximity of the mass to neurovascular and abdominal structures.
The most common location for metastatic disease to develop is in the lungs. The prevalence of distant metastases ranges from 6% to 37%.4, 6, 13 Metastases are more likely to develop in patients with higher-grade lesions and are almost universally present in patients with dedifferentiated lesions. Local recurrence and systemic metastases are independent predictors of poor overall survival.5
Some surgeons advocate curettage of low-grade lesions in the extremities. Curettage is often followed with adjuvant treatment of the cavity with phenol or cryotherapy. The adjuvant therapy serves to eradicate the microscopic disease, thus extending the surgical margin. Because of the high rate of recurrence and likelihood to dedifferentiate into a high-grade lesion, curettage is not recommended for pelvic lesions of any grade.
As previously mentioned, there are several histologic subtypes of chondrosarcoma: clear-cell chondrosarcoma, mesenchymal chondrosarcoma, and extraskeletal chondrosarcoma. The presentation, radiographic appearance, and prognoses of these rare variants differ from that of conventional chondrosarcoma.
Clear-cell chondrosarcoma was first described by Unni and associates in 1976. These lesions arise primarily in skeletally mature adults, most commonly in the third through sixth decade of life. The most common locations are the proximal humerus and the proximal femur.
Radiographically, clear-cell chondrosarcoma appears as a lytic lesion located in the epiphysis of a long bone.
Histologically, clear-cell chondrosarcoma lesions contain a combination of immature chondroid matrix surrounding chondrocytes with clear cytoplasm. The differential of this lesion is chondroblastoma, clear-cell sarcoma, and renal cell carcinoma. Some oncologists believe that clear-cell chondrosarcoma is the malignant counterpart of chondroblastoma.
Clear-cell chondrosarcoma is treated with wide local excision. The prognosis in patients with clear-cell chondrosarcoma tends to be better than for patients with other chondrosarcomas. These lesions can metastasize to the lung late; therefore, long-term follow-up for patients with pulmonary metastasis is warranted.
Mesenchymal chondrosarcomas arise both in bone (70%) and in the soft tissues (30%). It is most frequently found in adults in their third decade of life. The most common locations are the jaw, pelvis, spine, and scapula.
Radiographically, when occurring in bone, mesenchymal chondrosarcomas lesions are destructive (lytic) and often have stippled calcifications. Histologically, the tumor consists of immature cartilage matrix and aggregates of mesenchymal cells.
Surgical resection is the primary treatment for mesenchymal chondrosarcoma; however, in patients with a soft-tissue lesion, adjuvant chemotherapy and radiation may play a role. There is a high likelihood of metastases to the lung, lymph nodes (unlike conventional chondrosarcoma), and other osseous structures.
Prognosis for patients with mesenchymal chondrosarcoma is fair, with a 5-year survival after wide resection of 60% and a 10-year survival of 25%.
Chondrosarcoma can also arise in the soft tissue. These lesions are referred to as extraskeletal chondrosarcoma, or soft-parts chondrosarcoma.
Extraskeletal chondrosarcoma is quite rare, and the treatment regimen for this tumor is similar to that for other soft-tissue sarcomas. Radiation therapy (preoperative or postoperative) is used in conjunction with surgical resection. Chemotherapy may play a role in the treatment regimen.
Dedifferentiated chondrosarcoma was first described in 1971 by Dahlin and Beabout. The diagnosis is made histologically when a low-grade cartilage lesion is found in conjunction with a high-grade sarcoma.
Osteosarcoma is the most common type of associated high-grade malignancy. Radiographically, these lesions typically appear very aggressive with significant bony destruction.
The treatment regimen for dedifferentiated chondrosarcoma is similar to that for high-grade osteosarcoma—chemotherapy and surgical resection.
The overall prognosis for patients with dedifferentiated chondrosarcoma is poor. Although local control can often be surgically achieved, distant disease (lung metastases) develops in 90% of patients.14 The 5-year survival for patients with this lesion ranges from 0% to 18%.
Chondrosarcomas represent a diverse spectrum of diseases. They are tumors that should be treated with definitive and complete surgical resection if local control is to be achieved. Although grade 1 lesions in the extremity can be managed with curettage, incomplete surgical resection of intermediate and high-grade lesions puts the patient at risk for local failure, metastases, and eventual death.
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