Kaposi Sarcoma

Detailed Overview

It predominantly affects immunosuppressed individuals, most notably in the setting of advanced HIV/AIDS (Epidemic KS), but also occurs in solid organ transplant recipients (Iatrogenic KS) and classically in older men of Mediterranean/Eastern European descent (Classic KS). HHV-8 infection promotes massive angiogenesis and spindle cell proliferation.

Epidemiology & Demographics

Epidemic (AIDS-related) KS was historically the most common cancer in HIV patients. With modern antiretroviral therapy (ART), incidence has plummeted. Endemic KS is found in Sub-Saharan Africa. Classic KS is rare and indolent in older men.

Etiological Mechanism

Infection with Human Herpesvirus 8 (HHV-8), also known as Kaposi Sarcoma-associated Herpesvirus (KSHV), combined with immune dysfunction.

Primary Causes

HHV-8 infection (necessary but not sufficient on its own)

Profound immunosuppression (HIV/AIDS, CD4 count < 200)

Immunosuppressive medications (Post-transplant)

• HIV Infection: Specifically, poorly controlled HIV with CD4 counts < 200 cells/microL.
• Solid Organ Transplantation: Due to chronic use of calcineurin inhibitors and other immunosuppressants.
• Geographic/Ethnic background: Mediterranean, Jewish, or Middle Eastern descent for Classic KS.

HHV-8 targets endothelial cells. In the setting of impaired T-cell immunity, the virus expresses latent genes (e.g., LANA) and lytic genes that inhibit apoptosis, evade the immune system, and profoundly stimulate angiogenesis (via VEGF and inflammatory cytokines). This leads to the proliferation of abnormal, spindle-shaped endothelial cells forming slit-like vascular channels filled with red blood cells, resulting in the characteristic highly vascular, purple-red tumors.

Characteristic Clinical Presentation

• Skin lesions: Painless, non-pruritic, purple, pink, or brown macules, plaques, or nodules, often on the lower extremities or face.
• Oral lesions: Purple nodules on the hard palate or gums, leading to pain and difficulty eating.
• Edema: Severe lymphedema out of proportion to the size of the skin lesions, due to tumor invasion of lymphatic channels.
• Dyspnea and cough: Signs of pulmonary involvement, which can be rapidly fatal.

Physical Examination Signs

• Violaceous, non-blanching cutaneous nodules/plaques
• Woody edema of the lower extremities
• Hemoptysis (if pulmonary KS is present)
• Gastrointestinal bleeding (melena) if gut mucosa is involved

• Pulmonary Hemorrhage: Massive bleeding from pulmonary lesions leading to respiratory failure.
• Gastrointestinal Obstruction/Bleeding: Mass effect or ulceration of GI lesions.
• Immune Reconstitution Inflammatory Syndrome (IRIS): A paradoxical worsening of KS lesions shortly after starting HIV therapy.

Diagnostic Criteria & Guidelines

Clinical appearance confirmed by skin biopsy showing spindle cell proliferation, slit-like vascular spaces, extravasated RBCs, and positive immunohistochemical staining for HHV-8 LANA.

Differential Diagnosis

• Bacillary Angiomatosis (Bartonella infection)
• Angiosarcoma
• Melanoma
• Pyogenic granuloma

Laboratory Tests & Biomarkers

• HIV testing: Mandatory to rule out Epidemic KS.
• CD4 count and HIV Viral Load: Typically CD4 < 200 cells/microL and high viral load in AIDS-related KS.
• Tissue Biopsy with HHV-8 Staining: Positive for HHV-8 Latency-Associated Nuclear Antigen (LANA).

Imaging Modalities & Findings

• Chest CT: Nodular, reticular, or flame-shaped opacities extending along the bronchovascular bundles; pleural effusions are common in pulmonary KS.
• Upper/Lower Endoscopy: To evaluate for GI involvement if patient has unexplained anemia, melena, or abdominal pain.

• Good Risk (T0I0S0)
  Tumor confined to skin/nodes, CD4 > 150, no systemic illness.
• Poor Risk (T1I1S1)
  Tumor ulceration, severe edema, visceral involvement, CD4 < 150, history of opportunistic infections.

Second-Line & Adjunctive Therapy

For severe, rapidly progressive, or visceral KS: Systemic chemotherapy. Liposomal anthracyclines (Pegylated liposomal doxorubicin 20 mg/m2 IV every 3 weeks) are the standard of care. Paclitaxel is an alternative.

Surgical & Procedural Management

Surgery is rarely indicated due to the multifocal nature of the disease, but simple excision may be used for solitary annoying lesions.

Recommended Lifestyle Changes

• Strict adherence to ART to maintain a suppressed HIV viral load and high CD4 count.
• Use compression stockings and elevate legs to manage KS-associated lymphedema.

Patient Counseling & Advice

Warn patients starting ART that their lesions might temporarily get worse, swell, and become painful before they get better (IRIS phenomenon). Assure them this is a sign the immune system is waking up.

Follow-Up & Monitoring Schedule

Monitor CD4 and HIV viral loads every 3-4 months. Regular physical exams to monitor the size and number of lesions. Monitor cardiac function (ECHO) if taking liposomal doxorubicin.

Preventive Strategies

Safe sex practices to prevent HIV and HHV-8 transmission. Early initiation of ART for all HIV-positive individuals prevents the profound immunosuppression needed for KS to develop.

Highly dependent on immune status. With modern ART, the prognosis for Epidemic KS is generally good. Pulmonary KS remains a severe condition with significant mortality.