Chondrosarcoma is a malignant tumor whose cells produce cartilage. Chondrosarcoma can arise de nov (ie a primary tumor) or from malignant degeneration of benign cartilage lesions (such as enchondromas or osteochondromas). The incidence of Chondrosarcomas is highest in middle age; the pelvis is the most commonly location.
The average patient with chondrosarcoma presents with pain or an enlarging (painless) mass. In the pelvis, the presenting complaint can be related to obstruction of viscera by the mass effect of large tumors. Intrapelvic lesions can grow very large before they are notices and present as vague pain accompanied by urinary, sexual or bowel complaints.
In the long bones, especially in the setting of malignant transformation of an intramedullary lesion (eg, enchondroma), the presenting complaint is pain with use; this represents the destruction of cortical bone by the malignant cartilage and accordingly greater load on the remaining bone, producing pain. Rarely, fracture through the lesion is the initial presentation. Malignant transformation of osteochondromas (which, in contrast to enchondromas, typically grow on the surface of the bone) is characterized by noting that a known mass, stable in size for decades perhaps, has now begun to grow rapidly.
Patients with syndromes associated with multiple benign cartilage lesions, such as Olier’s Disease (multiple enchondromatosis), Maffucci’s Syndrome (multiple enchondromas and hemangiomas) and Multiple Hereditary Exostoses, are at elevated risk for malignant transformation. (One 1987 study reported that the incidence of secondary chondrosarcoma in patients who have Ollier disease is about 25 per cent by age forty, and that malignant degeneration is almost a certainty in patients who have Maffucci syndrome). Thus, patients with multiple benign lesions require lifetime surveillance for malignant transformation.
Rapid growth of a known skeletal mass is worrisome for malignant transformation of an osteochondroma
Chondrosarcomas are rare overall (the annual incidence in the United States is approximately 400 cases) but are the second most common primary musculoskeletal malignancy, representing approximately 20% of all such tumors.
Most patients are 50 years of age or older; a slight majority are male. Patients with secondary tumors from Ollier's disease or Maffucci's syndrome present in the third and fourth decade.
Pathology and pathophysiology
Chondrosarcomas reprenset the invasion of normal tissues by a malignant clone of cartilage cells. The microscopic findings are typically very reminiscent of normal cartilage; just too much of it, in the wrong place. Lobular nests of cartilage with varying degrees of cellular atypia are common. As the cellular atypia increases, the grade of the malignancy increases: the cells of a Grade 1 chondrosarcoma is similar to cells of normal cartilage; those of Grade 4 lesions are anaplastic and dedifferentiated. In between the cells of Grades 2 and 3 lesions, characterized by an increasingly proportion of abnormal-looking cells. The higher the grade, the more likely a tumor is to invade the surrounding tissues and spread to lymph nodes and other organs.
The differential diagnosis is relatively narrow for chondroid lesions. The diagnostic dilemma is at the interface between low grade (1/3) cartilage malignancies and benign cartilage tumors. Therefore the primary differential diagnosis is between chondrosarcoma and enchondroma, juxtacortical chondroma, and osteochondroma.
The causal mechanism for primary chondrosarcoma is unknown. The genes responsible for the premalignant lesions seen in Multiple Hereditary Exostoses have been identified as EXT-1 and EXT-2.
There is noted a predilection for chondrosarcoma in the central skeleton and some have theorised that the core body temperature could play a role in this though this is unproven.
Radiographic and laboratory findings
Radiographic studies show lesions in or on the bone which have production of chondroid matrix (ring and arc calcification) of varying degrees. Lesions tend to have pushing boundaries opposed to infiltrative boundaries.
Plain radiographs show calcified matrix lesions. The degree of calcification can indicate the relative age of the lesion and its maturation. Unmineralized areas of lucency especially adjacent to densely mineralized areas are worrisome for a relatively immature region of the lesion or a spindle cell area (secondary chondrosarcoma or dedifferentiated chondrosarcoma).
CT scan will show an invasive cartilage lesion with the typical stippled, popcorn or rings and arcs calcification. The lobular architecture may also be visible
MRI will show a lesion which is intermediate on T1 (with calcified areas being low signal) and a high signal lobular lesion on T2 (owing to the high water content of cartilage). Gadolinium enhancement will typically show peripheral enhancement in mature cartilage with immature cartilage malignancies having a heterogeneous enhancement pattern.
There are no characteristic laboratory findings
Risk factors and prevention
There are no identified risk factors beyond location. Central cartilage tumors should be followed clinically, radiologically or both for surveillance for malignant transformation.
The treatment for chondrosarcoma is surgical. The metabolic rate of cartilage is low and the inherent resiliencies of cartilage in low nutritional environments make chemotherapy ineffective. The typically low mitotic rate also makes radiotherapy less effective than in other sarcomas.
When possible, wide local excision is the treatment of choice for chondrosarcoma. There is a role for intralesional surgery (curetting and adjuvant) for low grade (1/3) intraosseous tumors with no soft tissue mass.
Metastasis develop in <15% of patients with grade 1 tumor and up to 50% of high grade lesions. Margin negative surgery has a good prognosis for local control and survival even in the pelvis ( 69% 5 yr, 59% 10 yr). However, the difficulty of margin negative surgery in the pelvis and spine leads to lower rates of local control and disease free survival.
Pelvic resections have a high morbidity and local recurrence rate. All sarcoma patients should have access to multidisciplinary care including nutrition, physical therapy and mental health support.
Histopathologically, there is a difference in grading a biopsy specimen depending on its location in the skeleton. Benign lesions in the phalanges can and often do exhibit binucleate lacunae and cellular atypia that would be called grade 2 chondrosarcoma in a specimen from the pelvis. Close coordination with a skilful musculoskeletal pathologist is recommended in every case of suspected chondrosarcoma.
Sarcoma, Enchondroma, Osteochondroma, Ollie’s Disease, Maffucci’s Syndrome, Multiple Hereditary Exostoses, EXT-1, EXT-2.
Skills and competencies
Medical students are encouraged to be able to recognize cartilage tumor matrix on a plain radiograph, identify normal cartilage on light microscopy and identify concerning features of a patient history with a growing skeletal mass.