Sarcomas are a rare and heterogeneous group of tumors that arise from mesenchymal tissues. According to the estimates of the American Cancer Society, approximately 1.6 million people were estimated to be diagnosed with cancer in the United States in the year 2013, with only 14,420, or just less than 1% of cases, representing sarcomas (1); 11,410 of these cases represent new soft tissue sarcomas and 3,010 represent bone sarcomas, with 4,390 and 1,440 deaths, respectively, resulting from these tumors (1).
EPIDEMIOLOGY AND PATHOGENESIS
The etiology and pathogenesis of sarcomas is not well understood. Multiple environmental factors including radiation and chemical exposures, trauma, and infection have been associated with the development of soft tissue and bone sarcomas. Both sporadic and inherited molecular and genetic aberrations have been identified in specific subsets of sarcoma and have been implicated in sarcomagenesis.
Several inherited familial cancer syndromes have been associated with a predisposition to development of soft tissue and bone sarcomas. The Li-Fraumeni syndrome resulting from a germline mutation of the p53 tumor suppressor gene is associated with increased risk of soft tissue sarcomas and osteosarcoma among several other cancers in children and young adults (2). Inherited retinoblastoma is also associated with the development of sarcomas, both osteosarcoma and soft tissue sarcoma (2). Neurofibromatosis type 1 is associated with an increased risk of development of sarcoma in a preexisting neurofibroma, resulting in a malignant peripheral nerve sheath tumor (3). Sarcomas have been associated with other cancer family syndromes including basal cell nevus syndrome, Werner syndrome, familial adenomatous polyposis, and Gardner syndrome, among others (2).
Recurrent cytogenetic abnormalities have been identified in many sarcomas and are thought to contribute to sarcomagenesis. Genetic profiling of bone and soft tissue sarcomas has expanded the characterization of mesenchymal tumors beyond translocation-positive/translocation-negative categorizations to identify three distinct groups: (1) genetically unstable sarcomas with complex karyotypes; (2) tumors with specific, recurrent genetic alterations such as translocations, deletions, or copy number variations; or (3) tumors with molecular aberrations such as amplifications, mutations, or loss of heterozygosity (Table 42-1). These alterations serve an important role in diagnosis as well as prognosis and have potential implications for therapy.
Table 42-1Genetic Alterations in Soft Tissue Sarcomas ||Download (.pdf) Table 42-1 Genetic Alterations in Soft Tissue Sarcomas
|Tumor ||Cytogenetic Abnormality ||Gene Product |
|Alveolar rhabdomyosarcoma || |
|Alveolar soft tissue sarcoma ||t(X;17)(p11.2;q25) ||ASPL-TFE3 |
|Clear cell sarcoma || |
|Congenital fibrosarcoma ||t(12;15)(p13;q25) ||ETV6-NTRK3 |
|Dermatofibrosarcoma protuberans ||t(17;22)(q22;q13) ||COL1A1-PDGFB |
Desmoplastic small round cell tumor
|Endometrial stromal sarcoma ||t(7;17)(p15;q11) ||JAZF1-SUZ12 |
|Gastrointestinal stromal tumor || |
Loss of 14q
LOH of 22q
Loss of 1p
KIT, PDGFR, BRAF
|Inflammatory myofibroblastic tumor || |
Low-grade fibromyxoid sarcoma