Soft Tissue Sarcoma

Soft tissue sarcomas are rare tumors that develop from the mesenchymal tissue layer, one of the three embryologic tissue types. The mesenchymal layer gives rise to deep skin tissues, blood vessels, fibrous tissues surrounding joints, cartilage, bone, smooth and striated muscles, and fat. Malignant tumors involving the peripheral nerves (ectoderm in origin) develop similarly and the treatment and outcomes are similar as well. The occurrence of soft tissue sarcoma in the United States is approximately 9,530 cases annually, which is only 0.7 percent of all malignant tumors. Of all the sarcomas 70 percent develop from soft tissue and 30 percent originate in bone.

Soft tissue sarcomas can be locally aggressive with direct extension to the surrounding tissues or can rarely metastasize (spread) to distant sites. The development of these sarcomas is thought to be malignant from the outset, that is, not developing from a benign lesion, which has undergone malignant transformation. Because these tumors are relatively rare and manifest in a multiplicity of histological subtypes and idiosyncratic biologic behavior, the natural history [Page 1580]and response to treatment is less than clear. As an example, according to the American Cancer Society 234,460 new cases of prostate cancer and 212,920 new cases of female breast cancer in America are estimated for 2006. In comparison, it is estimated that 500 cases of liposarcoma of the thigh will occur in 2006. The incidence of new prostate cancers is 468 times greater and new female breast cancers is 425 times greater than that of new thigh soft tissue sarcomas. These statistics indicate the limited numbers of patients who undergo various combinations of treatment so that it is difficult to determine which of the treatments is best.

Generally, there is no definite cause for soft tissue sarcomas but some factors do predispose for the condition, such as chronic irritation, lymphedema, genetic predisposition, radiation and/or chemotherapy exposure and chemical carcinogens. The occurrence of one specific type of sarcoma (Kaposi's sarcoma) is associated with the HIV and human herpes virus 8. Soft tissue sarcoma is classified as to the type of tissue from which the tumor developed. For example, sarcomas, which developed from fatty tissue, blood vessels, and striated muscle, would be termed liposarcoma, angiosarcoma, and rhabdomyosarcoma, respectively. Oftentimes it is not possible to determine the origin of the sarcoma and the sarcoma is named according to the structure seen on microscopy.

Grading the sarcoma based on examination under the microscope is useful in determining the aggressiveness of the tumor and the likelihood that the sarcoma may metastasize (spread to non-contiguous tissues). The lower grades of sarcomas are more likely to stay aggressive locally and less likely to metastasize.

Sarcomas are found throughout the body, including the extremities, retroperitoneum, head and neck, alimentary canal, genitourinary system, and uterus. The initial presentation of a soft tissue sarcoma is a palpable mass. The diagnosis of the type of soft tissue sarcoma can be made only with an adequate biopsy and special histological and immunohistological stains of the tissue.

The initial biopsy should be adequate for diagnosis and should be performed by a surgeon who is skilled in oncologic diseases. If the initial biopsy is not adequately performed, the later definitive surgery may have to involve the removal of larger areas than would have been initially required.

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