Definition

Kaposi's sarcoma is a type of cancer that arises from the cells lining the lymphatic or blood vessels. This malignancy originates from mutations in the cells of the skin or mucous membranes lining the gastrointestinal tract, spanning from the mouth to the anus (including the stomach and intestines). These mutated cells proliferate uncontrollably and can metastasize to other organs such as the lungs, liver, stomach, intestines, and lymph nodes.

Kaposi's sarcoma presents as raised patches or nodules on the skin and/or mucous membranes, such as the mouth, appearing in hues of purple, red, or brown. There are four types of Kaposi's sarcoma, classified by the affected demographic:

• Epidemic Kaposi's sarcoma (associated with HIV/AIDS)
• Classic Kaposi's sarcoma (Mediterranean)
• Endemic Kaposi's sarcoma (African)
• Transplant-related Kaposi's sarcoma

Causes

Kaposi's sarcoma is caused by infection with human herpesvirus 8 (HHV-8), also known as Kaposi sarcoma-associated herpesvirus (KSHV). This virus belongs to the same family as Epstein-Barr virus.

The exact process of infection and transmission of this virus remains unclear. It is suspected that HHV-8 spreads via saliva or genital secretions, possibly through sexual contact or mother-to-child interactions. Studies indicate that there are four groups of individuals more susceptible to Kaposi's sarcoma. Once the body’s cells are infected by the virus, these cells mutate and continue to divide. Cells that normally have a fixed lifespan keep growing, forming tumor tissues. Eventually, these cells transform into cancer cells.

Risk factor

A person must be infected with KSHV before developing Kaposi's sarcoma. However, most people infected with KSHV never develop Kaposi's sarcoma if their immune system is strong. Therefore, Kaposi's sarcoma generally occurs in individuals with compromised immune systems, such as:

• Those with HIV/AIDS
• Organ transplant recipients
• The elderly

Additionally, men are eight times more likely to develop Kaposi's sarcoma than women. In some regions of Africa, certain populations show signs of KSHV infection, making them more susceptible to Kaposi's sarcoma.

Symptoms

If untreated, most types of Kaposi's sarcoma will rapidly worsen within weeks to months, though some types progress very slowly over the years. Symptoms of Kaposi's sarcoma can include:

Skin abnormalities

The initial sign of Kaposi's sarcoma is often cancer-like spots on the skin. These spots can be purple, red, or brown, appearing flat with the skin, raised (plaques), or as nodules. Skin abnormalities most commonly appear on the legs or face but can occur anywhere on the body, often disrupting the skin's structure and appearance.

Lymph node swelling

Abnormalities on the legs or groin can impede fluid flow, causing painful swelling in the lymph nodes of the legs and feet.

Mucous membrane abnormalities

Signs of Kaposi's sarcoma may also appear on mucous membranes such as the mouth, rectum, gastrointestinal lining, and eye areas. These lesions typically do not cause pain or itching.

Organ abnormalities

Kaposi's sarcoma can also affect the lungs, obstructing airways and causing symptoms like coughing up blood and shortness of breath. If the cells mutate in the stomach or small intestine, digestive movement issues and gastrointestinal bleeding can occur, leading to anemia.

Diagnosis

Early diagnosis can improve outcomes and reduce the risk of the disease spreading to other organs. If Kaposi's sarcoma is suspected, the doctor will conduct a physical examination of the skin, mouth, and rectum, and check lymph nodes. Other diagnostic procedures may include:

Biopsy

In this procedure, a sample of abnormal tissue is taken and examined in a laboratory to determine if cancer cells are present. The abnormal tissue may be partially or entirely removed. If the abnormality is in the lungs or small intestine, specialized procedures like bronchoscopy or endoscopy are required to obtain the tissue sample.

Chest X-ray

Since Kaposi's sarcoma can spread to the lungs, a chest X-ray may be performed to examine the lungs. For patients with respiratory symptoms, a chest X-ray can determine if the disease is responding to treatment.

Internal examination

Bronchoscopy involves examining the airways and is recommended if the patient has symptoms like coughing up blood or shortness of breath, coupled with abnormal chest X-ray or CT scan findings.

Endoscopy is used to examine the esophagus, stomach, and duodenum. A colonoscopy is performed to view the colon. All these procedures involve inserting a flexible tube with a camera into the patient's body, usually under sedation. Any abnormal tissue is sampled for further laboratory analysis.

Management

The KSHV virus causing Kaposi's sarcoma cannot be eradicated. Once infected, the virus remains in the body permanently. Various treatment options exist for Kaposi's sarcoma, depending on several factors, such as:

• The type of Kaposi's sarcoma, to predict the disease's growth and spread rate
• The number and location of lesions (such as skin spots or mucous membrane abnormalities)
• The disruption caused by Kaposi's sarcoma
• The patient's medical condition, as some therapies might not be tolerated due to serious side effects

Enhancing the immune system

The primary treatment goal for Kaposi's sarcoma is to strengthen the immune system. Additional therapies, such as chemotherapy, are often poorly tolerated long-term in immunocompromised individuals.

The most effective and crucial treatment for Kaposi's sarcoma is addressing the immune weakness allowing the cancer to emerge. For HIV/AIDS patients, antiretroviral drugs used to manage HIV infection may also suffice to treat Kaposi's sarcoma. As their immune system improves, Kaposi's sarcoma symptoms may also subside.

For organ transplant recipients, adjusting or reducing the dose of immunosuppressive drugs might be considered.

Local therapy

Some doctors may recommend local therapy if the patient has only a few Kaposi's sarcoma skin lesions, such as:

• Radiation therapy
• Cryosurgery
• Topical retinoid therapy

Radiation therapy can also be applied to Kaposi's sarcoma tumors in the mouth or anus.

Chemotherapy

Patients who do not improve with immune-boosting therapies may require chemotherapy as a follow-up treatment. Chemotherapy is usually administered intravenously, although oral (pill) therapy is increasingly used.

Immunotherapy

This therapy activates the immune system's natural ability to better recognize and destroy cancer cells effectively.

Complications

Treatment typically prevents Kaposi's sarcoma from worsening. If the cancer has not spread to other organs, 82% of patients can live for at least five more years. This figure drops to 38% if the cancer has metastasized to distant organs.

Kaposi's sarcoma can cause severe or life-threatening issues when it grows in the lungs, liver, or gastrointestinal tract. For instance, Kaposi's sarcoma in the digestive tract can cause bleeding, while lung tumors can lead to breathing difficulties. Additionally, the cancer can spread to the lymph nodes and lungs.

Prevention

There is no vaccine to protect against HHV-8 infection. The best way to prevent Kaposi's sarcoma is to avoid factors that increase the risk of KSHV infection, such as unprotected sex.

For those with HIV, antiretroviral therapy can prevent Kaposi's sarcoma, especially if started when CD4 counts are still high. If you are in the advanced stages of HIV or have progressed to AIDS, testing for HHV-8 is available. Antiretroviral therapy can reduce the risk of developing Kaposi's sarcoma in HIV patients.

When to see a doctor?

You should consult a doctor if you have a weakened immune system and notice suspicious skin spots.

If Kaposi's sarcoma is suspected, your doctor will refer you for further testing to confirm the diagnosis.

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