Kaposi's Sarcoma

Kaposi's sarcoma (KS) is a type of cancer that manifests as masses on the skin, in lymph nodes, mouth, or other organs. It is characterised by painless, purple lesions that could be flat or raised.

Lesions can be isolated or widespread and may progress gradually or rapidly. Except for Classic KS, it results from immune suppression (e.g., HIV/AIDS) and infection by Human herpesvirus 8 (HHV8).

Types

KS has several sub-types:

• Classic KS: Typically affects older men in regions with high KSHV prevalence (Mediterranean, Eastern Europe, Middle East), usually involving the legs and progressing slowly.
• Endemic KS: Common in Sub-Saharan Africa, more aggressive in children, and older adults present similarly to Classic KS.
• Immunosuppression therapy-related KS: Generally occurs post-organ transplantation and mostly affects the skin.
• Epidemic KS: Occurs in AIDS patients, affecting multiple body parts.

Signs and Symptoms

Skin

Lesions are typically red, purple, brown, or black nodules or blotches, commonly found on the lower limbs, back, face, mouth, and genitalia. They may be plaque-like, especially on the soles of the feet, or cause skin breakdown leading to fungating lesions. Swelling may result from local inflammation or lymphoedema.

Mouth

Around 30% of cases involve the mouth, particularly the hard palate and gums. Lesions may bleed or develop secondary infections, interfering with eating or speaking.

Gastrointestinal Tract

Involvement in the gastrointestinal tract is common in transplant-related or AIDS-related KS. Symptoms may include weight loss, pain, nausea, vomiting, diarrhoea, bleeding, malabsorption, or intestinal obstruction.

Respiratory Tract

Respiratory involvement may present with shortness of breath, fever, cough, hemoptysis, or chest pain, often confirmed via bronchoscopy. Pulmonary Kaposi's sarcoma has a poor prognosis.

Cause

Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8) is present in almost all KS lesions. It encodes oncogenes, microRNAs, and circular RNAs that promote cancer cell proliferation and immune escape.

Transmission

In Europe and North America, KSHV is primarily transmitted through saliva, with kissing being a notable risk factor. Deep kissing among gay and bisexual men and the use of saliva as a sexual lubricant are significant transmission modes. KSHV can also spread via organ transplantation and blood transfusion.

Pathology

KS lesions contain spindle cells forming slits with red blood cells, giving a bruise-like appearance. The tumour is highly vascular, with abnormal blood vessels leaking red blood cells. Inflammation around the tumour may cause swelling and pain.

Diagnosis

KS diagnosis involves a biopsy and microscopic examination, with KSHV protein LANA detection confirming the diagnosis. Differential diagnosis includes arteriovenous malformations, pyogenic granuloma, and other vascular proliferations.

Treatment

Kaposi sarcoma is not curable but can be treatable for years. In KS associated with immunodeficiency, addressing the underlying immune dysfunction can slow or stop progression. HAART is very important for AIDS-associated KS, often leading to lesion shrinkage. Localised lesions may be treated with radiation therapy, cryosurgery, or topical beta-blockers like timolol. Widespread disease often requires systemic therapy with interferon alpha, liposomal anthracyclines, thalidomide, or paclitaxel.

Epidemiology

While the incidence of epidemic KS decreased with advanced HIV treatments, the number of people living with HIV/AIDS is rising, potentially increasing KS cases.

Society

KS brought public awareness as an AIDS-defining illness, notably depicted in the film "Philadelphia." KS is considered an opportunistic infection in AIDS, prevalent in regions with high KSHV prevalence like Sub-Saharan Africa.

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Self-assessment MCQs (single best answer)

Which virus is associated with Kaposi's Sarcoma?

What is a common characteristic of Kaposi's Sarcoma lesions?

Which type of Kaposi's Sarcoma is most commonly associated with AIDS?

Which of the following is NOT a common symptom of gastrointestinal involvement in Kaposi's Sarcoma?

What is the primary mode of KSHV transmission in Europe and North America?

Which treatment is very important for AIDS-associated Kaposi's Sarcoma?

What is a significant pathological feature of Kaposi's Sarcoma lesions?

Which sub-type of Kaposi's Sarcoma is most common in Sub-Saharan Africa?

What is a common site for oral lesions in Kaposi's Sarcoma?

Which of the following is NOT a typical treatment option for Kaposi's Sarcoma?