Kaposi’s sarcoma is caused by a virus called the human herpesvirus 8 (HHV-8), also known as the Kaposi’s sarcoma-associated herpesvirus (KSHV).

It’s thought this virus can alter the genetic instructions that control cell growth. This means some cells reproduce uncontrollably and form lumps of tissue known as tumours.

However, HHV-8 is a relatively common virus and not everyone who has it will develop Kaposi’s sarcoma. The virus only seems to cause the condition in some people with:

• a weakened immune system – this is thought to be the reason why people develop HIV-related Kaposi’s sarcoma and transplant-related Kaposi’s sarcoma
• an inherited (genetic) vulnerability to HHV-8 – this is thought to be the reason why people develop either classic Kaposi’s sarcoma or “endemic” African Kaposi’s sarcoma 

Read more about the types of Kaposi’s sarcoma.

How the virus is spread

Although HHV-8 was identified almost 20 years ago, there’s still no firm evidence about how it is spread. Some theories for how the virus spreads include:

• sexual transmission, particularly between men who have unprotected anal sex with other men
• saliva, possibly including kissing
• sharing needles and syringes used for injecting drugs
• from mother to baby during birth

However, more research is needed to determine exactly how the virus is spread.

Before diagnosing Kaposi’s sarcoma, your GP will ask you about your general health and carefully examine your skin.

If you have HIV or AIDS, the examination may be carried out by a member of your local HIV clinic who has experience of treating Kaposi’s sarcoma. They may take digital photos of any suspected lesions and send them to specialists, such as a cancer specialist (oncologist) or a skin specialist (dermatologist).

If it’s thought you may have Kaposi’s sarcoma, you’ll be referred for other tests to confirm the diagnosis, such as a skin biopsy.

If you don’t have HIV or AIDS, you will be referred to a specialist who treats skin cancer.

Further tests

Some of the tests used to diagnose Kaposi’s sarcoma are described below.

Biopsy

A biopsy is the most effective way of confirming a diagnosis of Kaposi’s sarcoma. It involves taking a small sample of cells from an affected area of skin, which is then checked for Kaposi’s sarcoma cells at a laboratory.

Read more about how a biopsy is performed.

Endoscopy

An endoscopy may be carried out if it’s thought you have Kaposi’s sarcoma in your digestive system. It involves inserting a thin, flexible tube called an endoscope down your throat.

This allows the specialist to look inside parts of your digestive system, such as your bowel, liver and spleen, for any abnormalities or signs of Kaposi’s sarcoma. A biopsy may be taken if anything suspicious is found.

If you have an endoscopy, you’ll be given a mild sedative to help you relax. A local anaesthetic will be sprayed on to your throat to prevent discomfort as the tube is passed down.

A similar method can be used to examine your lungs if it’s believed you have Kaposi’s sarcoma in your lungs. This is known as a bronchoscopy.

Imaging scans

A computerised tomography (CT) scan and/or a magnetic resonance imaging (MRI) scan may be recommended if it’s thought Kaposi’s sarcoma has spread to your lymph nodes or other parts of your body.

For example, you may have a CT or MRI scan if you have symptoms of breathlessness that may be caused by Kaposi’s sarcoma spreading to your lungs.

A CT scan works by taking a series of X-rays to build up a three-dimensional picture of the inside of the body. You may be given a radioactive dye to drink before the CT scan so that particular areas of your body can be seen in greater detail.

An MRI scan uses powerful magnets and radio waves to build up a detailed image of the inside of your body. Before having an MRI scan, you must tell your doctor if you have a pacemaker or any metallic implants in your body

Stages of Kaposi’s sarcoma

Staging is a medical term that describes how far a cancer has spread at the time it is diagnosed. The higher the stage, the more advanced the cancer and the further it has spread.

A number of different staging systems are used for Kaposi’s sarcoma. Some are specifically designed for specific types, such as HIV-related Kaposi’s sarcoma.

A staging system for all types of Kaposi’s sarcoma is outlined below:

• stage 1 – the cancer is limited to one section of the body, such as your legs, and there’s little or no spread inside your body
• stage 2 – the nodules have begun to grow upwards out of your skin, as well as deeper into the underlying layers of skin, damaging affected areas
• stage 3 – the cancer has spread into multiple lymph nodes but the internal organs, such as the lungs and digestive system, are unaffected
• stage 4 – the cancer has spread into the internal organs

Kaposi’s sarcoma is a rare type of cancer that can affect both the skin and internal organs.

The most common initial symptom of Kaposi’s sarcoma is the appearance of red or purple patches on the skin. The patches then grow into lumps known as nodules.

Kaposi’s sarcoma can also damage the internal organs, which can lead to a range of symptoms, depending on which organs are affected. These can include:

• breathlessness
• bleeding gums
• stomach pain
• leg swelling

Read more about the symptoms of Kaposi’s sarcoma and diagnosing Kaposi’s sarcoma.

Causes

Unlike most types of cancer, the cause for Kaposi’s sarcoma has been identified. The condition is caused by a virus known as the human herpesvirus type 8 (HHV-8), also called the Kaposi’s sarcoma-associated herpesvirus (KSHV).

HHV-8 is a relatively common virus. As many as 1 in 20 people may have the virus in their body, and in most cases it doesn’t cause any noticeable symptoms. The majority of people with the virus don’t develop Kaposi’s sarcoma.

However, certain groups of people who are vulnerable to the effects of HHV-8 go on to develop Kaposi’s sarcoma. These are usually people whose immune system isn’t working properly, either because of another medical condition or medication that suppresses the immune system. 

A weakened immune system allows the HHV-8 virus to multiply to high levels in the blood, which increases the chance that it will cause Kaposi’s sarcoma.

Read more about the causes of Kaposi’s sarcoma.

Types of Kaposi’s sarcoma

There are four main types of Kaposi’s sarcoma, which are outlined below.

HIV-related Kaposi’s sarcoma

Kaposi’s sarcoma often affects people whose immune systems have been severely weakened by HIV. This used to be a common condition in people with HIV, although advances in medical treatment mean it is much less widespread nowadays. It is thought that HIV causes HHV-8 to multiply, increasing the chance it will cause Kaposi’s sarcoma.

Kaposi’s sarcoma is sometimes referred to as an “AIDS-defining” condition. This means that this cancer occurs when HIV has damaged the immune system so much that it cannot protect a person from certain infections and cancers. This advanced stage of HIV infection is sometimes known as acquired immune deficiency syndrome, or AIDS.

Endemic African Kaposi’s sarcoma

Endemic African Kaposi’s sarcoma is common in parts of Africa and is one of the most widespread types of cancer in that region, accounting for 1 in every 10 cases of cancer in Africa.

Although this type of Kaposi’s sarcoma is classified separately from HIV-related Kaposi’s sarcoma, it’s highly likely that many cases are actually due to an undiagnosed HIV infection. In cases not related to HIV, it’s thought this type of Kaposi’s sarcoma develops due to a pre-existing genetic vulnerability to the HHV-8 virus.

Classic Kaposi’s sarcoma

Classic Kaposi’s sarcoma is a rare condition that mainly affects middle-aged and elderly men of Mediterranean or Ashkenazi Jewish descent. Ashkenazi Jews are people who are descended from Jewish communities that lived in central and eastern Europe. Most Jewish people in the UK are Ashkenazi Jews.

It is thought people who develop classic Kaposi’s sarcoma were born with a pre-existing genetic vulnerability to the HHV-8 virus.

Transplant-related Kaposi’s sarcoma

Transplant-related Kaposi’s sarcoma is a rare complication of an organ transplant. It occurs because medication to weaken the immune system (immunosuppressants) is used after a transplant to help prevent the body rejecting the new organ. However, this also makes the person more vulnerable to the HHV-8 virus.

Treating Kaposi’s sarcoma

The treatment for Kaposi’s sarcoma largely depends on which form of the condition you have. If it is only spreading slowly, treatment may not be immediately necessary.

If the condition spreads more rapidly and is causing severe symptoms, a number of treatments may be used. These can include surgery to remove small tumours and chemotherapy or radiotherapy to kill the cancer cells.

With proper treatment, Kaposi’s sarcoma can usually be controlled, and deaths from the condition in the UK are rare. However, it’s important to understand a complete cure for all types of Kaposi’s sarcoma isn’t always possible, and there’s a chance the condition could recur in the future.

Read more about treating Kaposi’s sarcoma.

The symptoms of Kaposi’s sarcoma vary depending on the parts of the body that are affected. The skin and internal organs are most commonly affected.

The skin

Any part of the skin, including inside the mouth, can be affected by Kaposi’s sarcoma.

Small, painless flat areas (lesions) usually develop first. The lesions can be different colours, including brown, red, blue and purple. They can look similar to bruises but, unlike bruises, they don’t lose their colour when they’re pressed.

The lesions are the result of many abnormal cell growths (tumours) affecting small blood vessels under the skin.

Lesions inside the mouth can make speaking and eating more difficult. They can also bleed if they are damaged when chewing.

Although Kaposi’s sarcoma growths usually start in one place, they can develop in more than one area. Over time, the growths may start to stick out of the skin and may merge into each other.

The internal organs

The internal organs most commonly affected by Kaposi’s sarcoma are the lymph nodes, lungs and the digestive system. The symptoms depend on which organs are affected.

When the lymph nodes are affected, there may be swelling in the arms and legs, which can be very painful and uncomfortable.

This is known as lymphoedema. It is caused by tumours blocking the flow of fluid through the lymph nodes. As a result, the fluid in the tissue backs up, causing swelling in the body’s tissues.

In cases where the lungs are affected, symptoms may include breathlessness and coughing up blood.

Where the digestive system is affected, symptoms can include feeling sick (nausea), vomiting, stomach pain and diarrhoea.

The treatment for Kaposi’s sarcoma depends on what type you have, your symptoms, how far the cancer has spread and your general health.

Many hospitals use multidisciplinary teams (MDTs) to treat Kaposi’s sarcoma. These are teams of specialists who work together to decide the best way to proceed with your treatment.

Deciding on the treatment that’s best for you can often be confusing. Your cancer team will recommend what they think is the best treatment option, but the final decision will be yours.

Before visiting hospital to discuss your treatment options, you may find it useful to write a list of questions you’d like to ask the specialist. For example, you may want to find out the advantages and disadvantages of particular treatments.

Treatment plans

Although the treatments used for Kaposi’s sarcoma usually differ from person to person, typical treatments for each form of the condition are outlined below.

HIV-related Kaposi’s sarcoma

Treatment for Kaposi’s sarcoma related to an HIV infection aims to reduce the HIV levels in the blood to allow the immune system to recover. This is so the levels of human herpesvirus 8 (HHV-8) in the blood are reduced so the Kaposi’s sarcoma will not recur. HHV-8 is the virus that causes Kaposi’s sarcoma.

If you have HIV-related Kaposi’s sarcoma, you will be given a course of combination antiretroviral therapy (cART) to reduce the amount of HIV in the blood to a very low or undetectable level.

As well as cART, you may require treatment with radiotherapy or chemotherapy, depending on the site and extent of the cancer and what symptoms it is causing.

Classic Kaposi’s sarcoma

As classic Kaposi’s sarcoma spreads slowly, immediate treatment isn’t usually required and a policy of “watchful waiting” may be recommended. This means your MDT will delay treatment to see whether any symptoms progress. This is often recommended for older people when it’s unlikely the cancer will affect their natural life span.

Radiotherapy is usually used if treatment is required, although small skin lesions may be removed using surgery or cryotherapy.

Endemic African Kaposi’s sarcoma

Endemic African Kaposi’s sarcoma is usually treated using a combination of radiotherapy and chemotherapy.

Transplant-related Kaposi’s sarcoma

Transplant-related Kaposi’s sarcoma is usually treated by reducing or stopping your current treatment with immunosuppressants (if possible), or with immunotherapy.

The aim is to strengthen your immune system enough to fight off the human herpesvirus 8 (HHV-8) while ensuring your body doesn’t reject the transplanted organ. It may take some time to find the best balance between these two treatment objectives.

If this method is unsuccessful, radiotherapy or chemotherapy may be used.

Treatments used

Some of the different treatments used for the various types of Kaposi’s sarcoma are described below.

Surgery

If the lesion is small, it may be removed using surgery. Your specialist will inject a local anaesthetic into the affected area to numb the lesions before they’re surgically removed.

Cryotherapy

Some small lesions can be removed using a treatment called cryotherapy. This involves freezing the lesions with liquid nitrogen.

Retinoic acid gel

Another treatment for small lesions is a gel called retinoic acid applied directly to the skin, usually several times a day. Up to half of people treated with retinoic acid experience an improvement in their lesions after a few weeks of starting treatment.

Common side effects of this treatment include mild irritation and redness.

Chemotherapy

Chemotherapy is where powerful medication is used to destroy cancer cells. It’s often used if the cancer has spread to more than one area.

The medicines can either be given through a drip into a vein in your arm (intravenously), or as a tablet. If the lesion is small, chemotherapy may be injected directly into it. This is called intralesional chemotherapy.

Chemotherapy can cause some significant side effects, including vomiting, temporary hair loss, tiredness and an increased vulnerability to infection.

To reduce the side effects, a type of treatment called liposomal chemotherapy may be used. In liposomal chemotherapy, the medicines are covered in a fat-based coating called liposome.

Radiotherapy

Radiotherapy uses high-energy rays to destroy cancer cells while doing as little harm as possible to healthy cells. It can be very effective in reducing the symptoms of Kaposi’s sarcoma affecting the internal organs, such as breathlessness and swelling of the arms and legs, and for Kaposi’s sarcoma affecting the soles of the feet.

Possible side effects of radiotherapy include:

• tiredness
• sore skin (particularly for people with advanced HIV infection)
• stiff joints and muscles
• feeling sick (nausea)
• temporary hair loss
• loss of appetite
• loss of libido (decreased interest in sex)
• early menopause in women
• temporary erectile dysfunction (inability to obtain or maintain an erection) in men

Most of these side effects gradually disappear after the course of treatment has been completed.

cART

Combination antiretroviral therapy (cART) involves the use of several different medications called antiretroviral therapy to lower HIV levels in the blood by slowing down the rate at which the virus can multiply.

Read more about treating HIV.

Immunotherapy

In immunotherapy (also known as biological therapy), special antibodies are created in a laboratory that work to change the make-up of cancerous cells so the immune system regards them as foreign objects. The immune system then starts to attack the cells in the same way that it would normally attack an infection.

Interferon alpha is an injected immunotherapy now only used rarely to treat Kaposi’s sarcoma because of the many side effects. It’s usually given by daily injections into the skin over a number of weeks.

Side effects of interferon alpha are common and can include:

• chills
• high temperature (fever) of 38°C (100.4°F) or above
• loss of appetite
• nausea
• headaches
• tiredness
• aching in the back, joints and muscles

Research into other treatments

Researchers are trying to discover effective treatments that could prevent Kaposi’s sarcoma from recurring.

One area of research is into targeted therapies. These are a group of medications designed to target and disrupt the functions of the HHV-8 virus, or enhance the immune response to weaken viral activity. However, there’s currently no evidence that any of these therapies work.

See clinical trials for Kaposi’s sarcoma to see how you can get involved with research into the condition.