Although Kaposi sarcoma (KS) initially was described over a century ago, its biology remains enigmatic and conflicting. Whereas the classic type occurs mainly in older men of Mediterranean or Eastern European backgrounds and is not linked to impairment of the host immune response, iatrogenic and human immunodeficiency virus (HIV)‐associated KS are linked to such conditions. A recently discovered pathogen, KS‐associated herpesvirus (KSHV) (also known as human herpesvirus 8 [HHV8]), is found in tissues from all four forms of KS (classic, iatrogenic, endemic [African], and HIV‐associated). This universal detection of KSHV/HHV8 suggests a central role for the virus in the development of KS and a common etiology for all KS types. The epidemiology and risk factors of classic KS, along with the biology of KSHV/HHV8 and the prevalence of the virus among different populations, is presented.

The current review is based on multiple information sources, electronic health data in all languages from 1966 onward, and previously published scientific reports from the Americas, Europe, and Africa.

Nearly 5000 cases of morphologically characterized classic KS have been reported in Europe, Mediterranean countries, and the Americas up to 1998. Geographic location, ethnicity, time interval, age, and gender heavily influence the incidence rate of classic KS. The rate of incidence of nonacquired immunodeficiency syndrome‐associated KS correlates with the KSHV/HHV8 seroprevalence in the general population.

Many contributory factors undoubtedly have etiologic and pathogenic significance in the development of classic KS; however, the interplay between these factors has complicated the understanding of the induction and development of the disease as well as the significance of each factor. As with other cell‐transforming human DNA viruses, infection with KSHV/HHV8 alone is not sufficient for the development of KS and additional cofactors are required. Cancer 2000;88:500–17. © 2000 American Cancer Society.