(Kaposi's Sarcoma; Multiple Idiopathic Hemorrhagic Sarcoma)
Kaposi sarcoma (KS) is a multicentric vascular tumor caused by herpesvirus type 8. It can occur in classic, AIDS-associated, endemic (in Africa), and iatrogenic (eg, after organ transplantation) forms. Diagnosis is by biopsy. Treatment for indolent superficial lesions involves cryotherapy, electrocoagulation, excision, or electron beam radiation therapy. Radiation therapy is used for more extensive disease. In the AIDS-associated form, antiretrovirals provide the most improvement.
(See also Overview of Skin Cancer.)
KS originates from endothelial cells in response to infection by human herpesvirus 8 (HHV-8). Immunosuppression (particularly by AIDS and drugs for organ transplant recipients) markedly increases the likelihood of KS in HHV-8–infected patients. The tumor cells have a spindle shape, resembling smooth muscle cells, fibroblasts, and myofibroblasts.
This form is the most common AIDS-associated cancer and is more aggressive than classic KS. Multiple cutaneous lesions are typically present, often involving the face and trunk. Mucosal, lymph node, and GI involvement is common. Sometimes KS is the first manifestation of AIDS.
This form occurs in Africa independent of HIV infection. There are 2 main types:
Cutaneous lesions are asymptomatic purple, pink, or red macules that may coalesce into blue-violet to black plaques and nodules. Some edema may be present. Occasionally, nodules fungate or penetrate soft tissue and invade bone. Mucosal lesions appear as bluish to violaceous macules, plaques, and tumors. GI lesions can bleed, sometimes extensively, but usually are asymptomatic.
Indolent lesions often require no treatment. One or a few superficial lesions can be removed by excision, cryotherapy, or electrocoagulation. Imiquimod has also been reported to be effective. Intralesional vinblastine or interferon alfa is also useful. Multiple lesions and lymph node disease are treated locally with 10 to 20 Gy of radiation therapy.
AIDS-associated KS responds markedly to highly active antiretroviral therapy (HAART), probably because CD4+ count improves and HIV viral load decreases; however, there is some evidence that protease inhibitors in this regimen may block angiogenesis. AIDS patients with indolent disease and CD4+ counts > 150/μL and HIV RNA <500 copies/mL can be treated with IV interferon alfa. Patients with more extensive or visceral disease can be given liposomal doxorubicin 20 mg/m2 IV q 2 to 3 wk. If this regimen fails, patients may receive paclitaxel. Other agents being investigated as adjuncts include IL-12, desferrioxamine, and oral retinoids. Treatment of KS does not prolong life in most AIDS patients because infections dominate the clinical course.
Iatrogenic KS responds best to stopping immunosuppressants. In organ transplant patients, reduction of immunosuppressant dosage often results in reduction of KS lesions. If dosage reduction is not possible, conventional local and systemic therapies used in other forms of KS should be instituted. Sirolimus may also improve iatrogenic KS.
Treatment of endemic KS is challenging and typically palliative.