STSs comprise a group of relatively rare, anatomically and histologically diverse neoplasms. These tumors share a common embryologic origin, arising primarily from tissues derived from the mesodermal or ectodermal germ layers, in contradistinction to carcinomas that arise from the endodermal germ layer. Although the somatic soft tissues account for as much as 75% of total body weight, neoplasms of the soft tissues are comparatively rare, accounting for 1% of adult malignancies and 15% of pediatric malignancies. The relative rarity of these tumors, coupled with the histologic diversity of tumors, has led to studies that often lump diverse tumors (STSs) into a single study group, making it difficult to develop specific therapies for specific tumor types, especially in adult STSs. The annual incidence of STSs in the United States is about 8300 new cases, comparable to the incidence of testicular cancer. However, an estimated 3900 patients die annually of soft-tissue sarcoma—a rate nearly 10-fold greater than is seen with testicular cancer—emphasizing the comparatively high overall mortality rate that is seen with this type of tumor.