A sarcoma (from the Greek ‘sarx’ meaning “flesh”) is a cancer of the connective or supportive tissue (bone, cartilage, fat, muscle, blood vessels) and soft tissue. This is in contrast to carcinomas, which are of epithelial origin (breast, colon, pancreas, and others).
Sarcomas are quite rare tumors, tumors that you don’t see that often. There are approximately 7,800 soft tissue sarcomas occurring in the United States, and this is about equivalent to the number of non-Hodgkin’s lymphomas, a little bit more than Hodgkin’s disease, but it’s a much rarer tumor than colon, lung, breast which are 170,000 to 180,000 a year. There can be the classical type of extremity and trunk, visceral involving the GI tract the GU tract, also KS and mesothelioma, and then even rarer are the bone sarcomas, approximately 2,600. The major one being osteogenic sarcoma but also chondrosarcoma, Ewing’s and MFH of bone. Although these tissues arise from about 75% of the average body weight, the just represent less than 1% of all adult and 15% of pediatric malignancies.
In terms of etiologies, exposure to radiation is certainly a cause of the development of sarcomas. Anywhere from 2000 to 7800 centigray and mostly we see osteogenic sarcomas, but also MFH, angio and fibrosarcomas. There is literature on chemical exposure and this comes from Vietnam and also from the farm belt in which exposure to herbicides and dioxin and oxyacetic acid can increase your chances of developing sarcoma. But there is quite a lot of debate in the literature about this. Also exposure to vinyl chloride and arsenic evolving into an angiosarcoma. Patients who’ve had renal transplants, chronic lymphocytic leukemia, autoimmune hemolytic anemia, can develop Kaposi’s. Then in terms of viral etiologies, the Kaposi’s sarcoma virus, HHV8, and also some literature looking at Epstein-Barr virus in children. Those children exposed to Epstein-Barr virus having a higher incidence of smooth muscle cell tumors. There is some literature, small usually, case reports of different injuries; scars, burns leading to fibrosarcoma. Implants and bone infarcts leading to osteogenic. There is the postmastectomy lymphedema, Stewart-Treves syndrome in which you develop an angiosarcoma. There’s a higher incidence of osteogenic sarcoma in those patients who have had Paget’s disease, and then certain benign forms of bone disease can also lead to osteogenic sarcoma.
In addition, in terms of genetic predispositions, those patients who have had a retinal blastoma develop about one thousand times more incidence of osteogenic sarcoma, and there is even a further risk if those patients have been exposed to radiation therapy. But you can also develop osteogenic sarcomas outside of the radiation therapy site. Rp53 17P _ in which there is a high incidence of sarcomas, breast, leukemia, brain tumors. The murine double minute 2, which is an oncogene on chromosome 12, and this can inactivate both P53 and a retinoblastoma and therefore gives you similar effects. Neurofibromatosis, a higher incidence when you have both a genetic defect of 17Q, where there would be a higher incidence of neurofibromas, and then adding on the P53 17P with an increased incidence of malignant schwannomas and neurofibrosarcomas. Also with Gardeners, the APC5Q, there is a higher incidence of intraabdominal desmoids.