William was an athletic, vigorous man who developed lower back discomfort.He thought, quite naturally, that it was caused by muscle strain or arthritis affecting the back, so he took anti-inflammatory drugs to ease the symptoms. The discomfort continued, however, and it worsened over several months, ultimately limiting his ability to move without pain.
William then sought medical attention and, about that time, developed a hard bulge that protruded from the lower back area on the right side. An MRI showed that the mass was growing in the lower back and buttock region and had its origin in muscles that run along the lower part of the spinal column. The mass was biopsied and proved to be a sarcoma. Neither William nor his wife had ever heard of sarcoma. This is not surprising, because sarcomas account for only 1 percent of adult cancers.
Sarcomas are cancers that derive from the supporting structures of the body (sarc is Greek for “fleshy,” and sarcoma means “fleshy growth”).
These supporting structures, or connective tissue, include muscle, bone, cartilage, fibrous tissue, fat, nerves, and blood and lymphatic vessels.
They give form, provide support, or supply nutrients to the human body and comprise the framework on which our vital organs and glands are built. For example, besides the glandular elements, the breast contains fat, muscles, ligaments, arteries, veins, and nerves that surround and support the glands and coordinate their function. Each connective tissue structure can give rise to a cancer that would be called a sarcoma, whether it occurred in the breast or another region of the body.
Physicians who treat sarcomas have divided the disease into two broad categories: those derived from bone and those derived from the soft tissues, such as fat or muscle. Osteosarcoma and Ewing’s sarcomaare the two most common bone sarcomas and affect children and adolescents more commonly than adults. Soft-tissue sarcomas occur most often in the extremities and abdomen, though they can arise virtually anywhere in the body. For example, sarcomas of the breast are well described but account for less than 1 percent of breast cancers.
Sarcomas and carcinomas have important differences other than originating from different cell types. Carcinomas typically metastasize to the lymph nodes, lungs, bones, liver, or brain. In contrast, sarcomas usually spread to fewer locations: those that originate in the abdomen metastasize mainly to other parts of the abdomen, whereas extremity sarcomas spread predominantly to the lungs. Some sarcomas may become very large and infiltrate surrounding tissues, making them difficult to remove completely. This may be apparent to the surgeon during the operation or be revealed on analysis of the specimen by the pathologist.
There are more than a hundred types of sarcomas. Many of the names are long and complicated but do bear some relation to the tissue they start in. For example, liposarcomas are derived from fat cells (lipos is Greek for “fat”), and angiosarcomas are derived from blood or lymphatic vessels (angos is Greek for “vessel”).
One sarcoma merits special attention because its treatment is unique among sarcomas. It is called GIST, which stands for gastrointestinal stromal tumor. GISTs are soft-tissue sarcomas that typically grow in the abdomen, most commonly in the stomach wall. Possible symptoms include pain, bleeding into the gastrointestinal tract, and abdominal swelling. GISTs that are not small and easily removed by surgery are incurable because they often spread throughout the abdomen. Before the late 1990s, GISTs were neglected cancers, considered to be rare and known to be resistant to chemotherapy and radiation therapy. No treatments could slow their growth, and survival was very limited. This situation changed dramatically with the discovery that the drug imatinib (Gleevec) could cause tumor regression in a high percentage of GIST sufferers.
The staging of sarcomas follows the TNM system, but as important as the stage is the “grade” of the tumor, because high-grade sarcomas have a much greater tendency to metastasize and limit survival compared with low-grade sarcomas. The treatment of sarcomas requires the combined input of an experienced surgeon, radiation oncologist, and medical oncologist to coordinate how surgery, radiation, or chemotherapy will be applied to lead to the best outcome. Referral to a specialized sarcoma center may be recommended.
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