Kaposi sarcoma

Also known as KS or multiple idiopathic pigmented hemangiosarcoma.

This is an AIDS-defining illness.
The name 'sarcoma' is a misnomer because a sarcoma should arise from mesenchyme tissue. The histogenesis of KS is unknown, but it is speculated to begin in lymphatic endothelial tissue.

 

Pathogenesis

• Human herpesvirus 8 (HHV-8) can establish lifelong infections in hosts.
• HHV-8 is an oncovirus. An oncoviral infection is sufficient to cause healthy tissue to become cancerous (oncogenesis). However, HHV-8 is rarely oncogenic in immunocompetent patients, due to immune system activity.
• In patients with immunosuppression, HHV-8 can activate oncogenes in infected cells.
• Highly vacular tumours form at sites of oncogenesis.

 

Risk factors 

• AIDS
• Post-transplant immunosuppression

 

Signs

Distribution

• Usually on the lower limbs, especially the toes and soles of the feet

Colouration:

• Red
• Violet
• Blue
• Black

Morphology: 

• Macule: flat area of altered colour, <1.5cm in diameter
• Patch: flat area of altered colour, >1.5cm in diameter

• Papule: solid raised palpable lesion <0.5cm in diameter
• Nodule: solid, raised, palpable lesion, >0.5cm in diameter
• Plaque: palpable, flat lesion, usually >1cm in diameter, most are raised, but some may just be thickened without being visibly raised, its borders may be well defined or poorly defined