Musculoskeletal ImagingSarcoma
a type of
tumour that is usually
malignant and usually arises from connective tissue, although some may originate in epithelial tissue. Various terms denote the type of tissue or structure involved, such as
cartilage (
chondrosarcoma), fibrous tissue (
fibrosarcoma), bone (
osteosarcoma), fat (
liposarcoma) and striated muscle (
rhabdomyosarcoma), among others (
Fig.1). These tumours are discussed more fully under their specific names.
Granulocytic sarcoma, also known as chloroma, represents a localized tumour mass composed of immature cells of the granulocyte series. The term chloroma reflects the frequently observed greenish colour of the tumour. Granulocytic sarcoma is associated most commonly with acute leukaemia of the myeloid type, especially in children. This type of sarcoma is more common in children than in adults and frequently involves bone, periosteum, soft tissue, orbit, lymph node and skin. Lytic lesions are characteristic of the bone involvement, which is especially prominent in the skull, spine, ribs, long tubular bones and sternum. In addition, soft tissue masses may erode the neighbouring bone.
Malignant tumours, especially osteosarcomas, are a well-recognized complication of radiation therapy. In some series fibrosarcomas have been the most common tumour noted, however. Malignant fibrous histiocytoma and chondrosarcoma have also occurred after radiotherapy. Osteosclerotic changes frequently precede the development of the sarcoma, and radiation osteitis is often present adjacent to radiation-induced tumours.
Certain solitary lesions in the tubular bones show a significant tendency to develop in specific osseous locations, such as the epiphysis (chondrosarcoma), metaphysis (osteosarcoma, chondrosarcoma) and diaphysis (Ewings sarcoma). Transarticular spread of epiphyseal tumours is encountered most consistently with aggressive lesions, such as bone sarcomas. Parosteal sarcomas develop from the periosteum.
Kaposis sarcoma is a tumour consisting of both capillaries and fibrosarcoma-like cells. This lesion predominates in men and occurs commonly in persons with acquired immunodeficiency syndrome AIDS .
Synovial sarcomas are uncommon malignant neoplasms intimately related to tendons, tendon sheaths, bursal structures and, less frequently, fasciae, ligaments, aponeuroses and interosseous membranes. On radiographs, a soft tissue mass is seen, sometimes with calcification or bone erosion or invasion.
Other types of sarcoma include clear cell sarcomas, which arise in the vicinity of tendons and aponeuroses of the upper and lower extremities; alveolar soft part sarcoma (malignant granular cell myoblastoma), usually found in muscles but may also appear in the orbit, retroperitoneum and elsewhere; and epithelioid sarcoma, a rare neoplasm arising principally in the fingers, hands and forearms of young adults.
A neurogenic sarcoma, also termed malignant schwannoma, may involve bone with soft tissue extension. This tumour occurs in patients with generalized neurofibromatosis.
DR/RB