Kaposi sarcoma is a malignant, multifocal, highly vascularized tumor of the endothelial cells that most commonly affects the skin but may also involve the lymph nodes, mucosa, and viscera. It is commonly associated with HIV and can occur at any CD4 count (typically < 500/mm3). Diagnosis is confirmed with biopsy. Treatment depends on whether the disease is localized or disseminated; all patients with HIV should be started on ART.
- Caused by human herpesvirus 8 (HHV8), a large DNA gamma herpes virus
- Routes of transmission include 
- Sexual contact
- Potentially via blood transfusion and IV drug use
Patients typically present with multiple cutaneous or visceral elevated tumors with rapid growth. 
- Most commonly affects the skin but may also involve the lymph nodes, mucosa, and viscera
- Can occur at any CD4 count; (typically < 500/mm3)
- Initial stage:
- Progression: may disseminate to the organs, particularly the gastrointestinal tract, respiratory tract, and lymph nodes.
Cutaneous lesions are the typical initial manifestation of KS. However, extracutaneous lesions (disseminated disease) can precede skin involvement. 
Subtypes and variants
- HIV/AIDS-associated KS (epidemic KS):
- Classic KS; : usually occurs in older Mediterranean or Eastern European men
- Iatrogenic KS; : usually occurs in immunosuppressed patients after organ transplants
- HIV screening
- Biopsy and histology of cutaneous or visceral lesions (indicated in all patients)
- CT with IV contrast: contrast-enhancement of lesions 
- Additional studies (depending on symptoms): Endoscopy and bronchoscopy may show red-purple lesions; hemorrhage may also be visible.
The decision to treat depends on whether the disease is localized or disseminated, as well as whether there is any underlying immunosuppression. Specialist consultation is recommended to determine the best course of management.
- Immunosuppressed patients: Manage underlying immunosuppression (first-line treatment).
- Immunocompetent patients or inadequate response to first-line therapy for immunosuppressed patients
Prognosis is variable, depending on subtype and whether disease is localized or systemic