Kaposi sarcoma (KS) is a malignant neoplasm of lymphatic endothelial cell origin that occurs in several forms: AIDS-associated and non-AIDS-associated. Subtypes of non-AIDS-associated KS include classic KS, African endemic KS, and iatrogenic KS. All types of KS are due to or influenced by human herpesvirus type 8 (HHV-8), and cutaneous findings are clinically and histologically indistinguishable among the types.

The outbreak of KS among young, previously healthy men who have sex with men (MSM) heralded the recognition of AIDS in 1981. AIDS-associated KS is the most common neoplasm in human immunodeficiency virus (HIV)-seropositive patients and is an AIDS-defining illness. This form of KS is primarily seen in the MSM population. Lesions may worsen during immune reconstitution inflammatory syndrome and may also appear in patients with HIV who have received long-term antiretroviral therapy (ART).

Lesions on the penis are common, and, in rare cases, the lesions may invade and penetrate the periurethral tissue, affecting urinary flow. The lesions are asymptomatic; however, large lesions may become eroded, cause pain, and form chronic ulcers.

The introduction of ART dramatically decreased the incidence, morbidity, and mortality of AIDS-associated KS. ART should be considered first-line treatment for AIDS-associated KS.