Chondrosarcoma

      Chondrosarcoma is a malignant tumor that produces cartilage matrix. Primary chondrosarcoma is very uncommon, arises centrally in the bone, and is found in children. Secondary chondrosarcoma arises from benign cartilage defects such as osteochondroma or enchondroma. Chondrosarcoma can also be classified as intramedullary, which generally arise from enchondromas, and surface which arise from osteochondromas. Chondrosarcoma occurs in the fifth or sixth decades and has a male to female ratio of 1.5 to 1. It is most common in the femur, humerus, ribs and on the surface of the pelvis. Patients with Ollier's disease (multiple enchondromatosis) or Maffucci's syndrome (multiple enchondromas and hemangiomas) are at much higher risk of chondrosarcoma than the normal population and often present in the third and fourth decade.
     The presentation of chondrosarcoma depends on the grade of the tumor. A high-grade, fast growing tumor can present with excruciating pain. A low grade, more indolent tumor is more likely to present as an older patient complaining of hip pain and swelling. Pelvic tumors present with urinary frequency or obstruction or may masquerade as "groin muscle pulls".
     On plain radiographs, chondrosarcoma is a fusiform, lucent defect with scalloping of the inner cortex and periosteal reaction. Extension into the soft tissue may be present as well as punctate or stippled calcification of the cartilage matrix. CT is helpful in defining the integrity of the cortex and distribution of calcification. MRI is invaluable in surgical planning as it demonstrates the intraosseus and soft tissue involvement of the tumor. MRI is also helpful in evaluating possible malignant degeneration of osteochondromas by allowing accurate measurements of the cartilage cap which should be less than 2 cm thick.
     On gross examination, chondrosarcoma is a grayish-white, lobulated mass. It may have focal calcification, mucoid I degeneration, or necrosis.Histologically, chondrosarcoma is differentiated from benign cartilage growths by enlarged plump nuclei, multiple cells per lacunae, binucleated cells, and hyperchromic nuclear pleomorphism. Chondrosarcoma is graded from 1 (low) to 3 (high). Low grade chondrosarcoma is very close in appearance to enchondromas and osteochondromas and has occasional binucleated cells. High grade chondrosarcomas have increased cellularity, atypia and mitoses. There is an inverse relationship between histologic grade and prognosis with higher grades having a worse prognosis and early metastases.
     There are three additional types of chondrosarcoma. Mesenchymal chondrosarcoma is a rare variant with a bimorphic histologic picture of low grade cartilaginous cells and hypercellular small, uniform, and undifferentiated cells that resemble Ewing's sarcoma. Mesenchymal chondrosarcoma has a predilection for the spine, ribs and jaw and it presents in the third decade. It is more common in females and can grow exceptionally large. It is very likely to metastasize to lungs, Iymph nodes and other bones.  Clear cell chondrosarcoma is a malignant cartilage tumor that may be the adult variant of chondroblastoma. It is a rare, low-grade tumor with an improved prognosis over other chondrosarcomas. Likechondroblastoma, it is found in the epiphysis of the femur and humerus. Histologically, soft tissue invasion is rare. Clear cell chondrosarcoma has clear cells with vacuolated cytoplasm. The cartilage matrix has significantly calcified trabeculae and giant cells. Dedifferentiated chondrosarcoma is the most malignant form of chondrosarcoma. This tumor is a mix of low grade chondrosarcoma and high grade spindle cell sarcoma where the spindle cells are no longer identifiable as having a cartilage origin. The dedifferentiated portion of the lesion may have histological features of malignant fibrous histiocytoma, osteosarcoma, or undifferentiated sarcoma. This biphasic quality is evident on x-ray with areas of endosteal scalloping and cortical thickening are contrasted with areas of cortical destruction and soft tissue invasion. Dedifferentiated chondrosarcoma has a 5 year survival of 10%. 
     Treatment of chondrosarcoma is wide surgical excision. There is a very limited role for chemotherapy or radiation. Biopsies must be planned with future tumor excision in mind. Patients with adequately resected low grade chondrosarcomas have an excellent survival rate. The survival of patients with high grade tumors depends on the location, size and stage of the tumor.

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Bulloughs, Peter, orthopedic Pathologv (third edition), Times Mirror International Publishers Limited, London, 1997.

Huvos, Andrews, Bone Tumors: Diagnosis, Treatment and Prognosis, W.B. Saunders, Co., 1991.