||BACKGROUND: Cutaneous soft tissue sarcomas (CSTS) are a heterogeneous group of mesenchymal neoplasms. To the authors' knowledge, no prior large, population-based study has focused on CSTS. METHODS: Surveillance, Epidemiology, and End Results (SEER) Program incidence and relative survival rates of CSTS were analyzed according to race, sex, and histologic type using the 2002 criteria of the World Health Organization classification. RESULTS: Among residents of the 13 SEER registries, 12,114 CSTS were diagnosed from 1992 through 2004. Overall age-adjusted CSTS incidence rates were highest among blacks (30.8 per 1,000,000 person-years) followed by whites (25 per 1,000,000 person-years), and American Indians/Alaska Natives (11.2 per 1,000,000 person-years) and were lowest among Asian/Pacific Islanders (7.7 per 1,000,000 person-years). Kaposi sarcoma (KS) accounted for 71.1% of cases, and the rates were similarly ranked. Dermatofibrosarcoma protuberans (DFSP) rates also were highest among blacks, whereas leiomyosarcoma (LS) and angiosarcoma (AS) rates were highest among whites. The rate ratio of men to women was 25.5 for KS, 4.7 for malignant fibrous histiocytoma (MFH), 3.7 for LS, 2.0 for AS, and 0.9 for DFSP. The 5-year relative survival rates were 99% for patients with DFSP, 89% for patients with MFH, 92% for patients with LS, and 45% for patients with AS. KS rates among men in the original 9 SEER registries increased more than 30-fold during the 1980s before they peaked around 1991 and subsequently declined rapidly because of human immunodeficiency virus-associated KS and highly active antiretroviral therapy. This KS pattern was evident not only among those ages 20 to 59 years but also among those ages 60 to 69 years. From 1978 through 2004, LS and AS rates among whites increased exponentially. CONCLUSIONS: CSTS rates varied markedly over time and by race, sex, and histologic type, supporting the notion that these histologic variants of CSTS areetiologically distinct.