Chapter 094. Soft Tissue and Bone Sarcomas and Bone Metastases (Part 6)

Chondrosarcoma Chondrosarcoma, which constitutes ~20–25% of all bone sarcomas, is a tumor of adulthood and old age with a peak incidence in the fourth to sixth decades of life. It has a predilection for the flat bones, especially the shoulder and pelvic girdles, but can also affect the diaphyseal portions of long bones. Chondrosarcomas can arise de novo or as a malignant transformation of an enchondroma or, rarely, of the cartilaginous cap of an osteochondroma. Chondrosarcomas have an indolent natural history and typically present as pain and swelling. Radiographically, the lesion may have a lobular appearance with mottled or...
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Chapter 094. Soft Tissue and Bone Sarcomas and Bone Metastases (Part 6) Chapter 094. Soft Tissue and Bone Sarcomas and Bone Metastases (Part 6) Chondrosarcoma Chondrosarcoma, which constitutes ~20–25% of all bone sarcomas, is atumor of adulthood and old age with a peak incidence in the fourth to sixthdecades of life. It has a predilection for the flat bones, especially the shoulder andpelvic girdles, but can also affect the diaphyseal portions of long bones.Chondrosarcomas can arise de novo or as a malignant transformation of anenchondroma or, rarely, of the cartilaginous cap of an osteochondroma.Chondrosarcomas have an indolent natural history and typically present as painand swelling. Radiographically, the lesion may have a lobular appearance withmottled or punctate or annular calcification of the cartilaginous matrix. It isdifficult to distinguish low-grade chondrosarcoma from benign lesions by x-ray orhistologic examination. The diagnosis is therefore influenced by clinical historyand physical examination. A new onset of pain, signs of inflammation, andprogressive increase in the size of the mass suggest malignancy. The histologicclassification is complex, but most tumors fall within the classic category. Likeother bone sarcomas, high-grade chondrosarcomas spread to the lungs. Mostchondrosarcomas are resistant to chemotherapy, and surgical resection of primaryor recurrent tumors, including pulmonary metastases, is the mainstay of therapy.This rule does not hold for two histologic variants. Dedifferentiatedchondrosarcoma has a high-grade osteosarcoma or a malignant fibroushistiocytoma component that responds to chemotherapy. Mesenchymalchondrosarcoma, a rare variant composed of a small cell element, also isresponsive to systemic chemotherapy and is treated like Ewings sarcoma. Ewings Sarcoma Ewings sarcoma, which constitutes ~10–15% of all bone sarcomas, iscommon in adolescence and has a peak incidence in the second decade of life. Ittypically involves the diaphyseal region of long bones and also has an affinity forflat bones. The plain radiograph may show a characteristic onion peel periostealreaction with a generous soft tissue mass, which is better demonstrated by CT orMRI. This mass is composed of sheets of monotonous, small, round, blue cells andcan be confused with lymphoma, embryonal rhabdomyosarcoma, and small-cellcarcinoma. The presence of p30/32, the product of the mic-2 gene (which maps tothe pseudoautosomal region of the X and Y chromosomes) is a cell-surface markerfor Ewings sarcoma (and other members of a family of tumors called PNETs).Most PNETs arise in soft tissues; they include peripheral neuroepithelioma,Askins tumor (chest wall), and esthesioneuroblastoma. Glycogen-filled cytoplasmdetected by staining with periodic acid–Schiff is also characteristic of Ewingssarcoma cells. The classic cytogenetic abnormality associated with this disease (and otherPNETs) is a reciprocal translocation of the long arms of chromosomes 11 and 22,t(11;22), which creates a chimeric gene product of unknown function withcomponents from the fli-1 gene on chromosome 11 and ews on 22. This disease isvery aggressive, and it is therefore considered a systemic disease. Common sites of metastases are lung, bones, and bone marrow. Systemicchemotherapy is the mainstay of therapy, often being used before surgery.Doxorubicin, cyclophosphamide or ifosfamide, etoposide, vincristine, anddactinomycin are active drugs. Local treatment for the primary tumor includessurgical resection, usually with limb salvage or radiation therapy. Patients withlesions below the elbow and below the mid-calf have a 5-year survival rate of 80%with effective treatment. Ewings sarcoma is a curable tumor, even in the presenceof obvious metastatic disease, especially in children Tumors Metastatic to Bone Bone is a common site of metastasis for carcinomas of the prostate, breast,lung, kidney, bladder, and thyroid and for lymphomas and sarcomas. Prostate,breast, and lung primaries account for 80% of all bone metastases. Metastatictumors of bone are more common than primary bone tumors. Tumors usually spread to bone hematogenously, but local invasion fromsoft tissue masses also occurs. In descending order of frequency, the sites mostoften involved are the vertebrae, proximal femur, pelvis, ribs, sternum, proximalhumerus, and skull. Bone metastases may be asymptomatic or may produce pain,swelling, nerve root or spinal cord compression, pathologic fracture, ormyelophthisis (replacement of the marrow). Symptoms of hypercalcemia may benoted in cases of bony destruction. Pain is the most frequent symptom. It usually develo ...