Chondrosarcoma is a primary malignant tumor derived from chondrocytes, and secondary chondrosarcoma can be formed when malignant transformation occurs on the basis of existing benign cartilage tumors (e.g. osteochondroma, endogenous chondrosarcoma). It is a typical adult tumor because of its prevalence between 30 and 70 years old, with an average age of 40-50 years old. Chondrosarcoma is more prevalent in men, with a male to female ratio of 1.5-2:1, and is widely distributed, commonly occurring in the pelvis, scapular girdle and proximal end of the long bones.
The common subtypes of chondrosarcoma are: clear cell chondrosarcoma, dedifferentiated chondrosarcoma, paracortical chondrosarcoma, mesenchymal chondrosarcoma, and secondary chondrosarcoma.
I. Etiology and pathology
The cause of chondrocytes originating from chondrocytes in bone or prechondrocytes of osteochondroma originating from outside of bone is still unclear.
Clinical manifestations
Chondrosarcoma is characterized by mild symptoms, slow development and long history. It often presents as a painful, slowly growing hard mass. Local pain and pressure are common symptoms, but a few patients may not have pain. Cases occurring in the spine, sacrum, ribs or pelvis can cause severe pain and may cause radiological pain due to nerve compression. In some cases, the tumor may suddenly and rapidly grow and invade soft tissues, producing severe pain. Chondrosarcoma of the spine and pelvis is difficult to palpate clinically because the lesion is deep and does not form a soft tissue mass in the early stage, but can form a huge soft tissue mass in the late stage.
Occasionally, tumors invade the joint cavity through the epiphysis causing joint symptoms, and pathological fractures are rare. Postoperative recurrent chondrosarcoma often shows stronger aggressiveness than the primary tumor.
Auxiliary examination
When it occurs in the medullary cavity, it may show cystic swelling changes, thinning of the cortex, uneven hairy inner surface of the cortex, irregular and uneven density of the cystic osteolytic area, and high density of dotted ring calcification or flocculent calcification within it. The edges are penetration-like, and there may be periosteal reactions and soft tissue masses.
2.Radionuclide scan: The area of nuclear concentration is larger than the extent of the lesion shown in the X-ray.
3.CT examination: CT examination of cancellous bone of the epiphysis and chondrosarcoma of the long diaphysis shows reliable calcification signs, and the detection rate is higher than that of plain film. The calcifications are round, semi-annular, scattered or aggregated, and the density is not uniform. The tumor can break through the cortex and protrude into the surrounding tissues to form soft tissue masses with infiltrative growth and unclear boundaries, and the masses in the iliac bone often protrude into the inner and outer pelvis, and the chondrosarcoma in the spine often invades into the spinal canal, and there are often calcifications in the soft tissue masses after CT enhancement.
4.MRI examination: T2-weighted scan is more sensitive to stromal calcification and soft tissue masses, and on T2-weighted image, calcification is low signal while tumor is high signal. Uniform high-signal hyaline cartilage is lobulated by low-signal fibrous spacer component, which can show ring and bow enhancement after Gd-DTPA injection enhancement.
5.Pathological examination.
(1) seen by the naked eye: blue-gray, translucent, slightly glossy tissue, interspersed with chalky or gray-yellow calcified areas, commonly with mucus-like cystic degeneration areas, non-calcified tissue with a hard and tough texture.
(2) Microscopic findings: the tumor cartilage was lobulated, with uneven cell distribution, hypertrophic nuclei, often with binucleated cells, and occasionally with irregularly shaped giant chondrocytes. The cell-matrix ratio varies according to the grade, which is moderate in low-grade malignant chondrosarcoma (G1) and increased in highly malignant (G2). Chondrosarcoma is mostly graded in three levels: low malignancy, moderate malignancy and high malignancy.
Diagnostic points
1. The main manifestations are painful, slowly increasing hard masses.
2.X-ray performance: it often shows osteolytic destruction, with penetrating edge, flocculent calcification and “scallop sign” of inner periosteum, and there may be periosteal reaction.
3. Examination shows that the cartilage is lobulated, with uniform cell distribution and hypertrophic nuclei, often with binucleated cells, and occasionally with irregularly shaped giant chondrocytes.
Differential diagnosis
1. Giant cell tumor of bone: it occurs mostly in the age of 20-40 years old, with localized soreness or pain, and the X-ray shows eccentric, osteolytic and expansive bone destruction located at the epiphyseal closure, often with soap bubble-like shadow, no calcification and surrounding bone shell formation. The main differentiation point with giant cell tumor is that there is no calcification in the lesion, no periosteal reaction, and mostly no soft tissue masses, which can be easily distinguished by pathological examination.
2. Bone cysts: they are mostly found in adolescents, with clinical manifestations of localized soreness or pain, mostly without clinical symptoms, mostly in the femur and upper humerus, with eccentric and osteolytic destruction, inconspicuous lobulation, surrounding osteosclerosis, and prone to pathological fracture. The main differentiation lies in the absence of calcification in the foci of bone cysts, clear margins, no periosteal reaction, no soft tissue masses, and easy differentiation by pathological examination.
The main symptoms are intermittent pain and swelling of adjacent joints and muscle weakness. x-ray shows a small round, low-density shadow of 2-4 cm in the center of secondary ossification with clear borders, surrounded by reactive bone to form a sclerotic margin, and punctate calcification can be seen in the lesion. The main differentiation is that chondroblastoma is a bone destruction in the center of secondary ossification, surrounded by reactive bone forming sclerotic margin, without periosteal reaction and soft tissue masses.
VI. Treatment and rehabilitation
1.Non-surgical treatment
(1) Radiotherapy: usually considered ineffective, occasionally used as temporary palliative treatment, only for pain relief.
(2) Chemotherapy: usually ineffective.
2.Surgical treatment
(1) Scraping and bone grafting: Since the success rate of scraping the lesion alone is very low, there is no indication for this surgical method regardless of the histological grade of the tumor. Only cases between chondrosarcoma and grade I central chondrosarcoma can be treated with an extended intra-focal resection, combined with local adjuvant therapy such as carbolic acid, 95% alcohol, liquid helium for wall inactivation, or bone cement filling.
(2) Amputation: Amputation can be considered for particularly large soft tissue masses, especially for grade III central chondrosarcoma and all “undifferentiated” chondrosarcomas. When recurrence occurs in the soft tissue after resection of chondrosarcoma, the tumor has no obvious boundaries, and generally cannot be treated by whole resection, amputation is required.
The local growth rate of the tumor and the incidence of lung metastasis depend on the malignancy of the tumor itself. Chondrosarcoma should be treated as early as possible, because although it grows slowly, sometimes its malignancy can increase or lead to “undifferentiation”. Grade I central chondrosarcoma is usually non-metastatic, but can recur locally if not extensively resected.
Grade II chondrosarcoma, despite its prolonged course and the fact that more malignant manifestations may not be observed histologically, can metastasize early and can easily recur locally. Grade III chondrosarcoma has the worst prognosis, with a survival rate of nearly 40%. The prognosis for “undifferentiated” central chondrosarcoma is very high, with a high rate of metastasis and early presentation even with extensive or radical surgery. Chemotherapy is usually ineffective. Radiotherapy can only be used to reduce pain.
The histologic malignancy of chondrosarcoma is sometimes difficult to clarify by preoperative biopsy, and the diagnosis can be determined during surgery by rapid frozen section examination, especially for rapidly developing, destructive and aggressive lesions. It is advisable to postpone surgery pending the results of pathological examination.