Kaposi sarcoma (KS) is a low-grade, multicentric, vascular neoplasm that was first described by Moriz Kaposi in 1872.¹ It is widely accepted that KS occurs in four clinical forms: classic, African endemic, epidemic, and idiopathic (transplant, immunocompromised-related).²,³ Classic KS is an indolent disease that most often occurs on the lower extremities of men of southern Mediterranean, eastern European, or Middle Eastern descent in the sixth decade of life.⁴,⁵ Risk factors associated with this form include never smoking, diabetes, and oral corticosteroid use.⁶ The male:female ratio is about 17:1, and the clinical course is usually mild, with only rare involvement of visceral organs.⁷,⁸

African endemic KS is a subtype that predominates in sub-Saharan Africa and is typically seen in young black HIV-negative men 25 to 40 years of age.⁹ There was a dramatic increase in KS since the onset of the HIV epidemic in Africa so that now it is the most common cancer among males and the second most common among females in Africa.¹⁰ Clinical manifestations vary from indolent to aggressive and lethal. There are four subtypes of endemic KS recognized: benign nodular, locally aggressive, disseminated, and lymphadenopathic. Lymphadenopathic is the most aggressive form, seen most often in African children aged 1 to 5 years.¹¹

Iatrogenic or posttransplantation, immunosuppressed-related KS occurs in patients following solid-organ transplantations treated with immunosuppression, or those on chronic immunosuppression for autoimmune disease.¹²,¹³,¹⁴,¹⁵,¹⁶ Risk factors include male sex, nonwhite race, lung transplant, HLA-B mismatch, and older age at the time of transplant. The incidence is highest within the first year after transplantation.¹⁷ Lesions are primarily limited to cutaneous involvement. Corticosteroids and cyclosporine A are the more common agents involved. Maintaining immunosuppression might be necessary for transplant patients to prevent organ rejection, but this can lead to further progression of iatrogenic KS. However, restoring immune defenses by reducing or discontinuing immunosuppression can often induce spontaneous tumor remission.¹⁸

The epidemic form of KS is the most common subtype, associated with the acquired immunodeficiency syndrome (AIDS), and is the most aggressive form of the disease. It frequently occurs in multiple locations involving the skin, mucous membranes, lymph nodes, and visceral organs including the gastrointestinal and pulmonary tracts.¹⁹ Before the 1980s, KS was a very rare tumor occurring primarily in the classic and iatrogenic forms. But since that time, the occurrence of KS has significantly increased, primarily as the AIDS-related epidemic form. Up to 30% of patients with HIV not taking highly active antiretroviral therapy (HAART) will develop KS.²⁰ Since the appearance of the epidemic form of KS, there have been sporadic case reports of this tumor in middle-aged HIV-seronegative homosexual males who have no evidence of immunodeficiency.²¹,²²,²³,²⁴ Clinical presentation in this group is similar to classic KS but occurs at a younger age. As with the classic form, cutaneous involvement usually involves the lower limbs, arms, genitals, and trunk. Also like the classic form, KS in this HIV-negative group runs an indolent course. This form has sometimes been recognized as a distinct subtype termed “nonepidemic KS.”¹⁹ A high percentage of patients with nonepidemic KS are positive for human herpesvirus-8 (HHV-8).²⁵,²⁶,²⁷