Kaposi Sarcoma: Causes, Symptoms, Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Kaposi sarcoma (KS) is a vascular tumor caused by human herpesvirus 8 (HHV-8, also called Kaposi sarcoma-associated herpesvirus, KSHV), arising from lymphatic endothelial cells that undergo oncogenic transformation via viral proteins including LANA, vFLIP, and vCyclin. Four epidemiological subtypes are recognized: (1) Classic KS: indolent disease in elderly Mediterranean or Ashkenazi Jewish men, typically confined to the lower extremities; (2) Endemic (African) KS: common in sub-Saharan Africa where HHV-8 seroprevalence is high, including aggressive lymphadenopathic variants in children; (3) Iatrogenic (transplant-associated) KS: occurs in solid organ transplant recipients on immunosuppression; and (4) AIDS-associated (epidemic) KS: the most common AIDS-defining malignancy in the pre-ART era, dramatically reduced by effective antiretroviral therapy. The introduction of combination ART in 1996 reduced AIDS-KS incidence by approximately 80% in high-income countries. KS lesions can involve skin, mucous membranes, lymph nodes, and visceral organs including the GI tract and lungs.

HHV-8 infection is the necessary and defining causative agent of all four subtypes of Kaposi sarcoma. HHV-8 is transmitted sexually (predominantly among men who have sex with men), through saliva, and vertically (mother-to-child in endemic regions). Once infected, HHV-8 establishes lifelong latency in B-cells and endothelial cells. KS development requires HHV-8 reactivation in a permissive immunological environment. HIV-induced CD4 T-cell depletion is the dominant immunological permissive factor for AIDS-associated KS, with KS risk inversely correlated with CD4 count (greatest risk below 200 cells/microL). Solid organ transplantation and associated immunosuppressive medications (calcineurin inhibitors, mycophenolate, corticosteroids) permit HHV-8 reactivation and KS development, typically within the first 2-3 years post-transplant. Classic KS occurs in age-related immune senescence in genetically susceptible individuals. In sub-Saharan Africa, endemic HHV-8 seroprevalence exceeding 50% in some populations, combined with any degree of immune compromise, drives the high incidence of African KS.

Cutaneous KS presents as violaceous (purple-red to dark brown-black) pigmented lesions ranging from flat macules to raised plaques or firm nodules. Lesions are typically multifocal, painless, and non-pruritic but may become painful with local trauma, ulceration, or superimposed infection. In AIDS-associated KS, lesions commonly involve the face (particularly the tip of the nose and periorbital region), trunk, upper extremities, and the hard palate and gingiva of the oral cavity. Oral KS may cause pain, difficulty eating, and tooth loss. Pulmonary KS causes progressive dyspnea, chronic cough, and hemoptysis, and may be life-threatening from respiratory failure or hemorrhage. Gastrointestinal KS most commonly affects the stomach and duodenum, causing iron-deficiency anemia from slow GI bleeding; large lesions cause pain, obstruction, or massive GI hemorrhage. Lymphatic involvement causes lymphedema — typically painful, progressive swelling of the lower extremities, genitalia, or face.

Skin biopsy is required for histological confirmation of KS. Histopathology reveals spindle-shaped tumor cells lining slit-like vascular spaces with extravasated erythrocytes, hemosiderin deposits, and variable inflammatory infiltrate. HHV-8 immunohistochemistry (anti-LANA-1 antibody, nuclear staining) is the most specific diagnostic marker. CD31 and D2-40 confirm endothelial/lymphatic endothelial differentiation. HIV testing is mandatory for all newly diagnosed KS patients. CD4 count and HIV viral load guide treatment planning for AIDS-KS. The AIDS Clinical Trials Group (ACTG) TIS staging system classifies AIDS-KS based on tumor extent (limited vs. extensive), immune status (CD4 greater or less than 150/microL), and systemic illness (presence of B-symptoms or OIs). Upper GI endoscopy or colonoscopy is performed when GI symptoms are present. CT chest-abdomen-pelvis assesses visceral involvement. Bronchoscopy with lavage evaluates pulmonary KS when chest CT shows bilateral pulmonary infiltrates.

For AIDS-associated KS, initiation or optimization of HIV antiretroviral therapy (ART) is the first and most important treatment step regardless of KS extent. ART-induced CD4 immune reconstitution alone induces regression of limited cutaneous KS in approximately 40-50% of patients. Immune reconstitution inflammatory syndrome (IRIS) — transient KS flare during early ART — is managed by continuing ART; systemic chemotherapy may be added. Local treatments for limited cutaneous lesions include intralesional vinblastine (0.1-0.2 mg/cm2), topical alitretinoin gel (9-cis-retinoic acid), cryotherapy, radiation (8 Gy single fraction or 20 Gy in 4 fractions for larger lesions), and laser therapy. Systemic chemotherapy for advanced KS: pegylated liposomal doxorubicin (PLD) 20 mg/m2 every 3 weeks is the preferred first-line regimen (ORR approximately 60%); paclitaxel 100 mg/m2 every 2 weeks is second-line for PLD-refractory KS. For transplant-associated KS, reducing immunosuppression and/or switching from calcineurin inhibitors to mTOR inhibitors (sirolimus) — which have direct anti-KS activity — is the initial treatment step. Pomalidomide shows activity in refractory AIDS-KS.

AIDS-associated KS prognosis has been transformed by effective ART. Five-year survival exceeds 70% for AIDS-KS patients on suppressive ART compared to under 20% in the pre-ART era. ACTG TIS good-risk criteria (T0/I1/S0 or S1: limited tumor, CD4 greater than 150/microL, no systemic illness) predict excellent response to ART alone or ART plus local therapy. Poor-risk criteria (T1: extensive tumor, lymphedema, GI/pulmonary involvement) require systemic chemotherapy but achieve median survival of 2-3 years with modern regimens. Classic KS is indolent with disease-specific survival of approximately 80% at 10 years. Endemic African lymphadenopathic KS in children carries the worst prognosis. Transplant KS may resolve with immunosuppression reduction.

Prevention of AIDS-associated KS rests on HIV prevention (condoms, pre-exposure prophylaxis with tenofovir/emtricitabine for high-risk MSM) and early ART initiation after HIV diagnosis. The dramatic reduction in AIDS-KS incidence since 1996 demonstrates that maintaining CD4 counts above 350 cells/microL through effective ART is the most powerful preventive measure. HHV-8 serology testing before solid organ transplantation identifies HHV-8-positive donors and recipients; HHV-8-seropositive transplant recipients require periodic surveillance for KS, particularly in the first 3 years post-transplant. Ganciclovir or valganciclovir (used to treat CMV in transplant recipients) may reduce HHV-8 replication and may offer incidental KS risk reduction. Regular skin examination in HIV-positive individuals and immunosuppressed transplant recipients allows early detection of cutaneous lesions when they are limited and most amenable to local treatment.

Any person with HIV who notices new purple, reddish, or brown skin lesions — particularly on the face, oral cavity, trunk, or extremities — should contact their HIV care provider immediately for evaluation. Do not assume skin lesions are benign in people with HIV without medical evaluation and biopsy when indicated. New purple lesions or discoloration on the hard palate or gums in an HIV-positive individual requires urgent dental or medical evaluation. Solid organ transplant recipients who develop persistent violaceous skin lesions or nodules at any time after transplantation should report these to their transplant team. Breathlessness, chronic cough, or blood in the sputum combined with known or suspected KS may indicate pulmonary involvement — a medical emergency requiring urgent chest imaging and pulmonology referral. GI symptoms including recurrent bleeding, unexplained iron-deficiency anemia, abdominal pain, or passage of dark stools in a patient with skin KS should prompt GI evaluation. Progressive leg swelling (lymphedema) in a patient with known KS warrants lymphatic involvement assessment and multidisciplinary care.