Kaposi’s sarcoma (KS)

Kaposi’s sarcoma (KS) is a malignant tumour arising from angio-formative cells, characterized by abnormal proliferation of vascular and lymphatic endothelial cells. It commonly originates in the skin but may involve multiple internal organs.

Kaposi’s sarcoma is associated with infection by human herpesvirus-8 (HHV-8) and occurs in different clinical forms. The disease may range from localized skin lesions to disseminated disease involving lymph nodes and visceral organs.

The four recognized types of Kaposi’s sarcoma include:

• Epidemic (AIDS-related) Kaposi’s sarcoma.

• Immunocompromised-associated Kaposi’s sarcoma.

• Classic or sporadic Kaposi’s sarcoma.

• Endemic (African) Kaposi’s sarcoma.

In the Tanzanian and African context, both endemic and AIDS-related forms are encountered. AIDS-related Kaposi’s sarcoma is the more common form, accounting for approximately 80–85% of cases.

Epidemiology

Kaposi’s sarcoma occurs worldwide but varies according to geographic distribution, prevalence of HHV-8 infection, and HIV burden.

AIDS-related Kaposi’s sarcoma is strongly associated with HIV infection and immunosuppression. Endemic African Kaposi’s sarcoma occurs independently of HIV infection and may affect children and adults.

Risk factors

Risk factors for Kaposi’s sarcoma include:

• Human herpesvirus-8 (HHV-8) infection.

• HIV infection.

• Reduced immune function.

• Immunosuppressive therapy following organ transplantation.

• Advanced immunodeficiency.

• Male sex.

• Endemic exposure in regions with high HHV-8 prevalence.

Pathophysiology

Kaposi’s sarcoma develops due to malignant transformation and proliferation of vascular endothelial cells associated with HHV-8 infection.

The virus promotes:

• Abnormal angiogenesis.

• Inflammatory cytokine release.

• Endothelial cell proliferation.

• Formation of vascular tumors.

In HIV-associated disease, immune suppression allows uncontrolled HHV-8 activity, resulting in more aggressive and widespread disease.

The tumour may involve:

• Skin.

• Lymph nodes.

• Gastrointestinal tract.

• Lungs.

• Other visceral organs.

Clinical presentation

Clinical presentation depends on the type of Kaposi’s sarcoma, immune status of the patient, and extent of disease.

Skin lesions are the most common presentation, but disseminated disease may occur, particularly in epidemic Kaposi’s sarcoma.

Symptoms

Cutaneous disease

• Dark brown skin lesions.

• Skin nodules.

• Skin plaques.

• Progressive enlargement of lesions.

Advanced or disseminated disease

• Fever.

• Night sweats.

• Weight loss.

• General weakness.

• Symptoms related to organ involvement.

Clinical signs

Typical findings include:

• Firm, dark brown nodules on the skin.

• Dark brown or violaceous plaques.

• Lesions commonly affecting the limbs.

• Multiple skin lesions.

• Generalized lymphadenopathy in children and immunodeficient patients.

• Skin lesions with or without lymph node involvement.

• Features of systemic disease.

B symptoms

Commonly associated with epidemic Kaposi’s sarcoma:

• Fever.

• Sweating.

• Weight loss.

Differential diagnosis

Conditions that may mimic Kaposi’s sarcoma include:

• Bacillary angiomatosis.

• Hemangioma.

• Angiosarcoma.

• Dermatofibroma.

• Melanoma.

• Cutaneous lymphoma.

• Chronic inflammatory skin lesions.

• Pigmented skin tumors.

Diagnostic criteria

Kaposi’s sarcoma should be suspected in patients presenting with:

• Firm dark brown or violaceous skin nodules.

• Skin plaques, especially on the limbs.

• Disseminated lymphadenopathy with or without skin lesions.

• B symptoms in patients with suspected epidemic Kaposi’s sarcoma.

• HIV infection with suspicious skin lesions.

Definitive diagnosis requires histological confirmation.

Investigations

Laboratory investigations

• Full blood count (FBC).

• Liver function tests (LFT).

• Urea.

• Creatinine.

• HIV test.

For HIV-positive patients:

• CD4 count.

• Viral load.

Imaging investigations

• Chest X-ray (CXR).

• Ultrasound of abdomen and pelvis.

• CT scan of abdomen and pelvis.

• CT scan of the chest.

Endoscopic evaluation

For suspected visceral involvement:

• Bronchoscopy.

• Endoscopy.

Histopathological investigations

• Skin biopsy for histological confirmation.

Diagnostic staging

Epidemic (AIDS-related) Kaposi’s sarcoma

Staged using:

• AIDS Clinical Trials Group (ACTG) staging system.

The ACTG system considers:

• Tumor extent.

• Immune status.

• Systemic illness.

Endemic and classical Kaposi’s sarcoma

Staged using:

• Mitsuyasu classification system.

Management

Treatment of Kaposi’s sarcoma is generally palliative regardless of disease type or stage. Management aims to:

• Control symptoms.

• Reduce tumour burden.

• Improve quality of life.

• Prevent complications.

Treatment selection depends on:

• Clinical presentation.

• Extent of disease.

• Immune status.

• Patient general condition.

Non-pharmacological treatment

Antiretroviral therapy (ART)

In patients with epidemic (AIDS-related) Kaposi’s sarcoma:

• Antiretroviral therapy should be initiated in patients who have not started treatment.

ART improves immune function and may result in regression of Kaposi’s sarcoma lesions.

Radiotherapy

Radiotherapy is the preferred palliative treatment for symptomatic patients with localized or extensive disease.

Radiotherapy schedules

For lesions involving limbs or lower half of the body:

• 8 Gy single fraction.

For lesions involving upper half of the body:

• 6 Gy single fraction.

For other sites:

• 9 Gy in 3 fractions.

OR

• 22 Gy in 11 fractions.

Pharmacological treatment

Palliative chemotherapy

Palliative chemotherapy is usually indicated for:

• Generalized disease.

• Extensive lesions.

• Symptomatic visceral involvement.

• Progressive disease.

Regimen 1: ABV regimen

Doxorubicin

• 25 mg/m² intravenously over 30 minutes on Day 1.

AND

Bleomycin

• 10 IU/m² intravenously over 10 minutes on Day 1.

PLUS

Vincristine

• 1.4 mg/m² intravenously over 10 minutes on Day 1.

Maximum vincristine dose:

• 2 mg.

Repeat every 21 days for 6–8 cycles.

Regimen 2

Paclitaxel

• 100 mg/m² intravenously on Day 1.

Repeat every 14 days.

Regimen 3

For persistent or recurrent disease after ABV:

Docetaxel

• 75 mg/m² intravenously on Day 1.

Repeat every 21 days.

Management according to underlying cause

Epidemic (AIDS-related) Kaposi’s sarcoma

Management includes:

• Initiation of antiretroviral therapy.

• Assessment of immune status.

• Radiotherapy for symptomatic lesions.

• Palliative chemotherapy for generalized disease.

Endemic (African) Kaposi’s sarcoma

Management includes:

• Symptom-directed treatment.

• Radiotherapy for localized symptomatic disease.

• Chemotherapy for extensive or progressive disease.

Immunocompromised-associated

Kaposi’s sarcoma

Management includes:

• Assessment and reduction of immunosuppression where possible.

• Symptomatic treatment.

• Specialist oncology management.

Referral

Patients with suspected or confirmed Kaposi’s sarcoma should be referred to specialized oncology and HIV care services for:

• Histological confirmation.

• Disease staging.

• HIV assessment and management.

• Selection of palliative treatment.

Urgent referral is required for:

• Rapidly progressive lesions.

• Extensive skin involvement.

• Suspected visceral involvement.

• Severe systemic symptoms.

Complications

Complications include:

• Extensive skin lesions.

• Lymphatic obstruction.

• Limb swelling.

• Pain.

• Bleeding from lesions.

• Gastrointestinal involvement.

• Pulmonary involvement.

• Respiratory symptoms.

• Reduced quality of life.

• Death in advanced disease.

Prognosis

Prognosis depends on:

• Type of Kaposi’s sarcoma.

• Immune status.

• Extent of disease.

• Presence of visceral involvement.

• Response to treatment.

AIDS-related Kaposi’s sarcoma may improve significantly with effective antiretroviral therapy and appropriate cancer-directed treatment. Advanced disseminated disease has a poorer prognosis.

Prevention

Prevention strategies include:

• HIV prevention measures.

• Early diagnosis and treatment of HIV infection.

• Early initiation of antiretroviral therapy.

• Prevention of immunosuppression where possible.

• Regular monitoring of immunocompromised patients.

• Early assessment of suspicious skin lesions.

Follow-up

Patients require regular follow-up to assess:

• Response to treatment.

• Disease progression.

• Recurrence.

• Development of visceral involvement.

• Treatment-related complications.

Monitoring should include:

• Clinical examination.

• Assessment of skin lesions.

• Evaluation of HIV status and immune function in HIV-positive patients.

• Imaging when clinically indicated.