Classification Approximately 20 different groups of sarcomas are recognized on the basis of the pattern of differentiation toward normal tissue. For example, rhabdomyosarcoma shows evidence of skeletal muscle fibers with cross-striations; leiomyosarcomas contain interlacing fascicles of spindle cells resembling smooth muscle; and liposarcomas contain adipocytes. When precise characterization of the group is not possible, the tumors are called unclassified sarcomas. All of the primary bone sarcomas can also arise from soft tissues (., extraskeletal osteosarcoma). The entity malignant fibrous histiocytoma includes many tumors previously classified as fibrosarcomas or as pleomorphic variants of other sarcomas and is characterized by a. | Chapter 094. Soft Tissue and Bone Sarcomas and Bone Metastases Part 1 Harrison s Internal Medicine Chapter 94. Soft Tissue and Bone Sarcomas and Bone Metastases Soft Tissue and Bone Sarcomas and Bone Metastases Introduction Sarcomas are rare 1 of all malignancies mesenchymal neoplasms that arise in bone and soft tissues. These tumors are usually of mesodermal origin although a few are derived from neuroectoderm and they are biologically distinct from the more common epithelial malignancies. Sarcomas affect all age groups 15 are found in children 15 years and 40 occur after age 55. Sarcomas are one of the most common solid tumors of childhood and are the fifth most common cause of cancer deaths in children. Sarcomas may be divided into two groups those derived from bone and those derived from soft tissues. Soft Tissue Sarcomas Soft tissues include muscles tendons fat fibrous tissue synovial tissue vessels and nerves. Approximately 60 of soft tissue sarcomas arise in the extremities with the lower extremities involved three times as often as the upper extremities. Thirty percent arise in the trunk the retroperitoneum accounting for 40 of all trunk lesions. The remaining 10 arise in the head and neck. Incidence Approximately 9220 new cases of soft tissue sarcomas occurred in the United States in 2007. The annual age-adjusted incidence is per 100 000 population but the incidence varies with age. Soft tissue sarcomas constitute of all cancers in the general population and of all cancers in children. Epidemiology Malignant transformation of a benign soft tissue tumor is extremely rare with the exception that malignant peripheral nerve sheath tumors neurofibrosarcoma malignant schwannoma can arise from neurofibromas in patients with neurofibromatosis. Several etiologic factors have been implicated in soft tissue sarcomas. Environmental Factors Trauma or previous injury is rarely involved but sarcomas can arise in scar tissue resulting from a prior operation .
