Chondrosarcoma is a malignant bone tumor derived from chondrocytes, and its tumor cells have the characteristic of producing cartilage. There are two types of chondrosarcoma: primary and secondary. Primary chondrosarcoma is more common, accounting for about 60% of cases. Secondary chondrosarcoma is relatively rare and is caused by the malignant transformation of chondrosarcoma or osteochondroma. According to the location of tumor, it can be divided into central, peripheral and paracortical (periosteal) chondrosarcoma. According to the histological characteristics of the tumor, it can be classified into general, clear cell, mesenchymal and dedifferentiated chondrosarcomas. The most common type of chondrosarcoma in clinical practice is the primary type of central chondrosarcoma.
I. Clinical characteristics
1. Age
It occurs mostly in adults aged 30 to 60 years old, and rarely develops before 20 years old.
2. Gender
There are more male patients than female patients, and the ratio is about 1.5 to 2:1.
3.Site
It occurs in the long bone epiphysis and trunk bones of the limbs, and is more common in the proximal and distal femur, proximal humerus, proximal tibia, pelvis, scapula, etc. It rarely occurs in the metacarpals and phalanges.
4.Symptoms and signs
Chondrosarcoma has a slow onset and mild clinical symptoms, and is often detected only when the mass is large. Secondary chondrosarcoma can last for several years or even a dozen years. Occasionally, rapid onset, severe pain, and rapid progression of the disease can be seen, and the clinical course is similar to that of osteosarcoma, mostly in adolescent patients.
The main clinical manifestations are local pain and masses, which are mild at the beginning and gradually worsen. Examination may reveal a hard mass with pressure pain. If the mass is large, it may affect the movement of joints, and there may be an increase in skin temperature and subcutaneous venous anger. The central type mostly starts with pain and gradually appears as a mass, while the peripheral type starts with a mass and is less painful or painless.
Imaging characteristics
1.X-ray performance
The typical X-ray manifestation of chondrosarcoma is to show scattered speckle-like or mass-like calcification shadows in the lesion of different sizes. In the long bone epiphysis, there is extensive osteolytic destruction with blurred boundary and swollen bone cortex, and sometimes the soft tissue mass shadow can be formed by tumor penetration. Calcified spots may appear in the osteolytic area or soft tissue shadow, and the periosteal reaction is not obvious.
2. CT and MRI
CT and MRI are not specific, but they can help to define the scope of tumor invasion and determine the surgical plan.
Pathological changes
1.Major body
The tumor tissue is grayish white and translucent with slight luster, the surface is uneven, and pseudofibrous tissue envelope may appear. The tumor is lobulated and brittle in the cross-section, with common calcification or ossification foci. Sometimes mucus-like changes and cystic changes occur in the mass, and jelly-like material flows out.
2.Microscopic
Chondrosarcoma is composed of sarcomatous chondrocytes and cartilage matrix, often accompanied by intrachondral calcification and ossification. If the differentiation is good, the chondrogenic cells are located in the stromal sockets, with relatively small nuclei, regular shape, sparse cell arrangement and more cartilaginous stroma; if the differentiation is poor, the cell size and morphology are extremely inconsistent, with larger nuclei, which can be shuttle-shaped, triangular or polygonal, and nuclear division and tumor giant cells are common. The tumor cells are dense, the stroma is relatively reduced, and foci of calcification are rare. The tumor is often separated into many lobules by fibrous tissue.
Differential diagnosis
1.Endogenous chondrosarcoma
It is sometimes difficult to distinguish chondrosarcoma with low malignancy and good differentiation from endogenous chondrosarcoma with active growth, which must be analyzed together with clinical, X-ray and microscopic pathological changes. Endogenous chondrosarcoma is usually found in the short bones of hands and feet, with small size, regular shape and mild pain.
2. Mucinous fibroma of cartilage
Chondrosarcoma with mucous-like changes needs to be differentiated from mucous-like fibroma of cartilage. The former is more painful, with a large and irregular lesion that penetrates the bone cortex and is accompanied by a large soft tissue mass without a surrounding sclerotic margin. Histological examination can generally confirm the diagnosis.
3.Osteosarcoma
Chondrosarcoma in adolescents has a rapid progression and severe pain, and needs to be differentiated from osteosarcoma. Osteosarcoma can be seen microscopically as direct osteogenesis by tumorigenic osteoblasts or spindle cells, while chondrosarcoma shows intrachondral ossification.
V. Treatment and prognosis
The main treatment is surgery. Early extensive or radical resection with good borders can achieve satisfactory results. If the lesion is small in extent or the histological examination is good, local wide excision of the tumor and large bone graft or artificial bone joint replacement can be used; if the lesion is extensive and adheres to the surrounding important blood vessels and nerves and the cell differentiation is poor, amputation or joint dissection can be performed; for chondrosarcoma occurring in the pelvis, hemipelvic resection and artificial joint replacement can be considered. For chondrosarcoma occurring in the pelvis, hemipelvic resection and reconstruction with artificial prosthesis can be considered. Chondrosarcoma is not sensitive to chemotherapy and radiotherapy, but radiation therapy can be tried in areas where surgery cannot be performed to control tumor growth and reduce pain.
The prognosis of chondrosarcoma is good, with a five-year survival rate of about 50% to 70%. The prognosis is related to the degree of differentiation of the tumor. Most of the secondary chondrosarcomas have higher degree of cell differentiation, so the prognosis is good.
Special types of chondrosarcoma
1.Paracortical (periosteal) chondrosarcoma
Paracortical (periosteal) chondrosarcoma is a malignant chondrogenic tumor located on the bone surface, which is less common. It is mostly seen in men aged 10-30 years old, and the common sites are the bone surfaces of femur, tibia and humerus. The clinical manifestation is a hard, fixed, relatively painless, slow-growing mass, which is mostly found unintentionally. Radiographic findings: The lesion is located on the surface of the long bones, usually at the epiphysis. Early stage tumors are often non-calcified and show soft tissue density shadow. Late stage tumors are more calcified. There is no translucent gap between the tumor and the adjacent bone as in parosteal osteosarcoma. There is usually no periosteal reaction.
Pathological manifestations: Paracortical chondrosarcoma is a tumor that lies on the bone surface and grows into the surrounding soft tissues, usually without invading the adjacent bone. Its texture and appearance resemble that of mature cartilage. It appears as a grayish, lobulated, tough lesion in the uncalcified portion and chalky in the calcified area. Histologic features seen microscopically are similar to those of the usual type of chondrosarcoma. Most are low-grade malignant lesions with good tissue differentiation and may exhibit some degree of cellular anisotropy.
Treatment: For stage I paracortical chondrosarcoma, a safe surgical border can be obtained by extensive local excision without the need for amputation. For stage II or recurrent stage I lesions, radical resection should be considered. The prognosis is better than that of central chondrosarcoma
2.Chondrosarcoma of mesenchymal type
Mesenchymal chondrosarcoma is a rare malignant chondrogenic tumor. It occurs in 10-30 years old and is more common in men. The site of occurrence is spine, ribs and pelvis, and about 1/3 occurs in extraosseous soft tissue.
Patients present with chronic pain, swelling and soft tissue masses.
Pathological manifestations: The tumor appears as grayish-red, soft, fish-like tissue. The characteristic histological features seen microscopically are: diffuse dense undifferentiated or hypodifferentiated mesenchymal cells interspersed with islands of highly differentiated cartilage.
Mesenchymal chondrosarcoma should be differentiated from Ewing sarcoma.
Treatment requires radical resection or amputation, and radiotherapy or chemotherapy is feasible for those who cannot be operated.
3.Destructive chondrosarcoma
Dedifferentiated chondrosarcoma is a low-grade malignant or junctional cartilage tumor that has been differentiated into other sarcomas with high mesenchymal changes, such as fibrosarcoma, malignant fibrous histiocytoma or osteogenic sarcoma. It occurs in middle-aged and elderly people aged 50 to 75 years old, and is more common in men. The site of origin is the pelvis and scapular girdle. This type of chondrosarcoma is characterized by rapid growth, severe bone destruction, early lung metastasis, and a 2-year survival rate of less than 20%.
Patients present with a sudden increase in size and pain of a previously painless mass. Low-grade malignant chondrosarcoma may undergo dedifferentiation several years after the onset of disease, thus exhibiting a clinical course of explosive bone destruction.
Radiographic manifestations: lobulated calcified lesions with a slow growth pattern (characteristic of the chondrogenic component) are seen. A large hypodense soft tissue component is also seen as a dedifferentiated portion. CT typically shows flocculent calcification in the cartilaginous component mixed with low-density foliated tissue in the fibrous component.
Pathological manifestations: The cartilage area is grayish translucent, with a fish-like appearance in the cell-rich areas. Microscopically, cytologic features were seen as low-grade malignant (G1), active, cell-rich and mature cartilage lobules that abruptly transformed into highly malignant (G2) areas of spindle cells. The fibrous component presents as a fibrosarcoma or malignant fibrous histiocytoma with more nuclear divisions. When the sampling material for excisional biopsy is located in the periphery, the central cartilage component is easily lost, and puncture biopsy may result in false impressions because only the cartilage component is obtained due to the small sampling material. Differentiated chondrosarcoma should be differentiated from chondrogenic osteosarcoma.
Treatment requires radical resection or amputation to achieve local control. After extensive resection, there is a high rate of local recurrence. Marginal resection, on the other hand, usually leads to local recurrence. Radiotherapy or chemotherapy is available for those who cannot be operated.
4. Clear cell type chondrosarcoma
It is a rare, low-grade malignant tumor arising from immature cartilage tissue. It occurs in the bony ends of long bones, especially the proximal humerus and femoral head. Patients often present with slowly progressive pain, which can last up to five years prior to presentation.
Radiographically, the tumor appears as a swollen osteolytic destruction of the long bone ends or epiphysis, surrounded by a thin layer of reactive bone. The imaging resemblance to a benign tumor and the lack of calcification often make it easy to confuse with chondroblastoma or giant cell tumor of bone.
CT examination: Osteolytic lesions with thin cortical bone-like margins surrounded by contrast-enhanced images and occasional faint calcifications may suggest this diagnosis.
Pathological examination: the tumor tissue is grayish-red, soft and brittle, and can be gritty, with occasional small congested cystic cavities. Microscopically, lobulated lesions were seen. The tumor cells were large in size with abundant transparent cytoplasm and centrally located nuclei, and nuclear division was rarely seen. The nucleus is centrally located and nuclear division is rarely seen. Slender lines of calcification are seen between the hyaline cells, showing “lattice calcification” and trabecular bone-like tissue. There are benign multinucleated giant cells in the middle of the lesion.
Clear cell chondrosarcoma should be distinguished from giant cell tumor of bone, chondroblastoma and chondrogenic osteosarcoma.
Treatment is the same as that for general chondrosarcoma.
Typical case 1: Male, 40 years old, right hemipelvic chondrosarcoma
Pre-operative X-ray
Preoperative CT
Postoperative X-ray
Typical case 2: male, 60 years old, clear cell chondrosarcoma of the neck of the right femur
Pre-operative X-ray
Pre-operative MRI
Post-operative X-ray