Kaposi sarcoma is a rare tumor. There are several types of Kaposi sarcoma and the most common type has links to advanced HIV.
Before the spread of HIV in the United States, KS was extremely rare. However, by the early 1990s, the incidences of KS had increased 20-fold. The numbers in the U.S. have reduced significantly since then due to improved treatment for HIV. However, this type of cancer still most commonly develops in people with stage 3 HIV, or AIDS, as well as those taking immunosuppressant medications.
In this article, we look at the different types of KS, what causes them, and how to treat this type of tumor.
KS is a multicentric vascular tumor. This means that it affects blood vessels and can develop on soft tissue in multiple areas of the body at once.
It originates in the endothelial cells that line blood vessels and lymphatic vessels. KS allows these cells to grow at a faster rate and survive for longer than usual.
People with weaker immune systems have a high risk of Kaposi sarcoma. This includes people with HIV, individuals who are taking medication to suppress the immune system after an organ transplant, and older adults whose immunity has declined with age.
KS causes tumors to develop on the skin, in the mouth, or other parts of the body, such as the lymph nodes or lungs. When KS affects the skin, lesions often appear on the legs or face. These lesions are usually harmless. However, KS lesions on the liver, digestive tract, or lungs are typically more severe.
Almost all KS lesions contain viral DNA from KSHV. KSHV has several modes of transmission. It can spread through sexual and non-sexual contact, including through organ transplantation and saliva.
There are four main types of KS:
- Epidemic KS: This is the most common form of KS. This type develops in people who have a diagnosis of stage 3 HIV. Doctors consider KS to be an AIDS-defining illness. This means that once a person develops KS, it is likely that they will have a diagnosis of AIDS rather than HIV. However, some people with well managed HIV and an undetectable viral load still develop KS.
- Classic KS: This occurs mainly in older adults of Eastern European, Mediterranean, and Middle Eastern descent. Men experience classic KS more than women. This type presents lesions that grow more slowly than other types.
- Endemic KS: Also known as African KS, this form is relatively common in equatorial Africa. It generally develops in people under 40 years of age. This used to be the most common type of KS in Africa, but with the increase in AIDS incidence throughout Africa, epidemic KS is now the most widespread.
- Latrogenic KS: This is also known as transplant-related KS. People may develop this type after taking drugs that suppress the immune system after an organ transplant. If a person carries KSHV, taking immunosuppressant medications may cause them to develop KS.
People with KS do not always present signs or symptoms. In many people, however, skin lesions more clearly indicate the presence of the disease.
KS often presents as marks on the skin with the following characteristics:
- brown, purple, pink, or red blemishes, or macules
- the tendency to merge into plaques and nodules that range from blue-violet to black
- occasional swelling and outward growth or inward growth into the soft tissue or bone
The macules, plaques, or tumors may appear to be blue or violet if the tumor is a mucosal lesion. This is a lesion of mucosal tissue, such as tumors of the mouth or throat.
A gastrointestinal KS lesion may cause bloody stools. These lesions are typically symptomless. Rarely, they may lead to pain, diarrhea, or physical obstruction.
If KS affects the lining of the lungs, it can cause breathlessness due to blockage. A bleeding lesion on the lung may leak blood into the mucus, which the individual then coughs up.
The different types tend to have different presentations:
- Epidemic KS: This is more aggressive than other types and usually produces multiple lesions, often on the face and trunk. People with endemic KS typically develop Internal tumors.
- Classic KS: This usually results in a small number of lesions, usually on the skin of the lower limbs and particularly on the ankles and soles of the feet. The skin lesions grow more slowly than in other types of KS. People with classic KS rarely develop internal tumors.
- Endemic KS: Some forms of endemic KS appear identical to classic Kaposi, while other types affect the lymphatic system and internal organs.
- Latrogenic KS: This can appear more suddenly. Lesions usually remain on the skin, but this is not always the case.
A laboratory examination of a sample can help a doctor confirm a suspected KS lesion on the skin. They will usually collect this sample using a punch biopsy, which may require a local anesthetic.
If a doctor suspects that a person might have internal KS tumors, such as in people with stage 3 HIV, they may use other tests, including:
- CT or X-ray scans of the chest and abdomen
- gastrointestinal endoscopy
There is no routine method for identifying KS, and often more than one lesion can appear at the same time. This can make it difficult for doctors to detect an isolated tumor early.
People who are at risk, such as those with a suppressed immune system, may undergo regular checks for KS.
Doctors use specific, officially authorized systems to stage most cancers. However, when staging the progression of KS, they use the AIDS Clinical Trials Group (ACTG) system.
The ACTG system looks at:
- the extent of the tumor
- the status of the immune system
- the extent of involvement within the body or systemic illness
Many people do not experience any pain from their tumors and do not require treatment.
However, the treatment options for KS are similar to those doctors recommend for other types of cancer. These include:
Treatment for KS focuses on maintaining the health of the immune system. This typically involves targeting HIV or using immunosuppressant drugs.
Antiretroviral therapy (ART) is a combination of anti-HIV drugs that make treatment for KS more effective. A doctor may recommend them as part of combination therapy alongside chemotherapy.
This is relevant only to people with stage 3 HIV who also have KS tumors. This treatment aims to improve a person’s immunity by reducing the HIV load.
People with suppressed immune systems due to medication can manage KS by switching or decreasing their drug regimen.
Local therapies for KS include:
- surgical excision, in which a surgeon removes a lesion using a scalpel or curette
- cryotherapy, in which a surgeon attempts to freeze the lesion off of the skin using liquid nitrogen
- electrocoagulation, in which a skin specialist uses electricity to destroy a lesion
When multiple lesions affect lymph nodes, a doctor typically applies radiation therapy directly to the lesions.
Healthcare professionals sometimes recommend imiquimod cream for treating superficial tumors, such as in people with classic KS. This cream combats viruses and strengthens the immune system.
A doctor might inject some chemotherapy drugs, such as vinblastine, directly into the tumor.
However, many people experience undesirable side effects with vinblastine. As a result, researchers are investigating other types of localized treatment, such as sodium tetradecyl sulfate. A doctor may recommend intravenous (IV) chemotherapy drugs for more aggressive forms of KS.
Immunotherapy for KS triggers the immune system to attack cancer cells. Interferon-alpha is one form of immunotherapy. A medical professional injects interferon into muscle tissue.
The American Cancer Society uses the 5-year survival rate to measure how likely it is a person will live for 5 years beyond a diagnosis of KS when compared to a person who does not have cancer.
They suggest that people who detect and treat KS before it has spread to nearby areas have an 81% chance of living for 5 or more years after diagnosis.
However, this reduces to 45% for people whose KS lesions have spread to distant parts of the body, such as the lungs.
People with compromised immune systems should follow the advice of their doctor concerning regular screening for KS.
Where do KS lesions most commonly develop?