3.3.8 Kaposi’s Sarcoma

Kaposi sarcoma is a rare disease (<10 cases/1000 patients) but is more common in HHV8 endemic areas (Mediterranean, African) and in immunocompromised subjects.

Kaposi’s sarcoma is associated with HHV8 infection. Immunosuppression (solid organ transplant, HIV) is a well-known risk (and prognostic) factor. A genetic disposition may play a role as familial cases of Kaposi’s sarcoma have been observed.

Characteristic findings include blue-red (purple) macules, plaques or tumours on the skin and mucosae. Lymphoedema is also common.

Kaposi sarcoma is classified into four types:

• Classic Kaposi’s sarcoma, typically in older men in Southeastern Europe and the Mediterranean basin

• Endemic (African) Kaposi’s sarcoma appears primarily in patients from sub-Saharan Africa

• HIV-associated (epidemic) Kaposi’s sarcoma is frequently found in advanced stage of HIV infection in men who have sex with men (MSM)

• Kaposi’s sarcoma in immunosuppressed patients (iatrogenic) may occur for example in solid organ transplant recipients

Biopsy is mandatory for the diagnosis. It shows a proliferation of spindle-cells sometimes with mild to moderate cytologic atypia, forming vascular and pseudovascular structures dissecting between collagen fibres, often mixed with a variable chronic inflammatory infiltrate. Kaposi sarcoma cells stain for endothelial cell markers such as CD34 and CD31. The identification and localisation of HHV8 within Kaposi lesional cells using a monoclonal antibody against HHV-8 latent nuclear antigen (LANA) is the most diagnostically helpful immunostaining technique available to differentiate Kaposi from its simulators because it is specific for Kaposi sarcoma.

The clinical course depends on the type of the Kaposi sarcoma. Owing to its slow progression and indolent biologic behaviour, classic Kaposi sarcoma does not seem to impact the mortality rate.

Classic and endemic Kaposi sarcoma are rarely associated with nodal or visceral involvement. The HIV- associated and iatrogenic Kaposi sarcoma are more frequently associated with visceral involvement.

Diagnosis is obtained by clinical features, anamnesis, histology, and detection of HHV-8. A total body CT scan +/- lung and digestive endoscopies can be performed depending on the clinical form.

Reduction of the immunosuppression is important in HIV-associated and iatrogenic Kaposi sarcoma: antiretroviral therapy is used as first-line in HIV-associated Kaposi sarcoma. In iatrogenic forms, the optimisation (decrease) of the immunosuppressive medication (and switch to mammalian Target Of Rapamycin (mTOR) inhibitors) must be considered. In classic Kaposi sarcoma, no treatment is needed in many cases. Surgery or laser may be used to destroy lesions. Radiotherapy, intralesional chemotherapy and electrochemotherapy have high response rates. Topical treatments— imiquimod or topical 9-cis-retinoid acid—can also be used. Systemic treatments are reserved for locally aggressive extensive and disseminated Kaposi sarcoma: the recommended first-line agents are pegylated liposomal doxorubicin and paclitaxel. In classical Kaposi sarcoma pegylated liposomal doxorubicin or pegylated interferon-alfa are the recommended first-line agents in younger patients.