Kaposi's sarcoma (KS) is a type of cancer that can form purplish masses (tumors) on the skin, in the mouth, in lymph nodes, and in other organs. There are different types of KS, some of which cause tumors to develop and spread rapidly, and others that are slow growing and even short-lived.

KS is typically associated with advanced human immunodeficiency virus (HIV) infection, but there are other types that can affect groups of people without HIV.

The common thread that connects all of these types is a weakened immune system coupled with an infection by a virus known as human herpesvirus 8 (HHV8). The underlying cause of a weakened immune system largely determines how aggressively or slowly KS symptoms develop.

This article looks at the common signs and symptoms of Kaposi's sarcoma and takes a deeper dive into how the symptoms and complications vary by the different KS types.

Common Symptoms

Kaposi's sarcoma is a rare type of cancer known as a sarcoma that causes the formation of tumors in soft tissue, such as bones, tendons, muscles, ligaments, cartilage, and fat.

With KS, the disease develops from cells called endothelial cells that line the blood vessels. It is considered angioproliferative because it spreads (proliferates) through blood vessels (with "angio" meaning blood vessels in Greek). While KS usually causes tumors on the skin, it can sometimes spread to internal organs.

The defining features of KS are the characteristic skin tumors that can also affect the gums and mouth. Among the tell-tale signs are:

• KS tumors most commonly affect the lower limbs, back, face, mouth, gums, and genitals.
• KS tumors usually start as small, flat lesions with a brown, blue, red, or purplish color, often looking like little bruises.
• KS lesions do not blanch (whiten) when pressed.
• KS lesions are typically painless and not itchy.
• The lesions can occur on their own, cause multiple lesions on one part of the body, or be widespread.
  
• As the tumors spread, they can converge into larger masses and sometimes turn into elevated lumps, called nodules.
• Even though KS lesions and nodules are painless, they can sometimes form ulcers and bleed. This is especially true of KS tumors in the mouth.
  

Rare Symptoms

For some people, KS may be limited to certain parts of the body (such as the lower legs) and never progresses. However, in rare cases, KS can spread from the skin to the internal organs. This scenario is likely in people with AIDS, the most advanced stage of HIV infection.

In people with AIDS, the immune system has been so weakened that a person is considered immunocompromised (meaning lacking adequate immune defense). Without these defenses, diseases like cancer can become invasive and infiltrate organs more readily.

The organs most commonly affected are those of the lymphatic system. The lymphatic system is a network of vessels and organs that, among other things, is responsible for trapping and neutralizing disease-causing agents in the body.

The three organs of the lymphatic system most commonly affected by KS are:

• Lymphatic vessels: In addition to blood vessels, KS can spread through lymphatic vessels that transport a fluid called lymph throughout the body. Tumors that form in these vessels can block the flow of lymph and cause the abnormal, painful swelling of tissues known as lymphedema. The lower legs are most commonly affected.
• Lymph nodes: KS can also cause tumors in the lymph nodes that act as the filters of the lymphatic system. The formation of tumors combined with the onset of inflammation can cause lymphadenopathy (swollen lymph nodes). With lymphadenopathy, the lymph nodes may be visibly swollen, red, and tender or painful to the touch.
• Spleen: Less commonly, KS can affect the spleen, an organ that helps to filter blood. KS in the spleen can often lead to splenomegaly (an enlarged spleen). In addition to discomfort, pain, or fullness in the upper left side of the abdomen, splenomegaly can cause fatigue, unintended weight loss, and radiating pain to the left shoulder

Complications/Subgroup Indications

The complications and symptoms of Kaposi's sarcoma can vary by the type of KS a person has. The four broad categories are:

• HIV-associated Kaposi's sarcoma: Also known as epidemic KS, this is an aggressive form affecting people with advanced HIV infection.
• Classic Kaposi's sarcoma: This is an indolent (slowly progressing) form mainly affecting older males of Mediterranean or Eastern European descent.
• Transplant-related Kaposi's sarcoma: Also known as iatrogenic KS, this is a typically treatable form affecting organ transplant recipients on immunosuppressant drugs.
• Endemic Kaposi's sarcoma: This is a type seen in young African men and African children (the latter of which is associated with an increased risk of death).
  

Complications of HIV-Associated KS

With HIV-associated KS, tumors can spread to different organs of the body, such as the digestive tract, lungs, liver, and heart.

The symptoms can vary by which organ systems are involved, including:

• Digestive tract: Kaposi's sarcoma of the digestive tract, called gastrointestinal KS, is the most common form of internal KS. Symptoms include abdominal pain, fatigue, cramping, nausea, vomiting, bloody stools, and rapid weight loss. The majority of people with gastrointestinal KS will also have skin lesions. In rare cases, gastrointestinal KS can lead to bowel obstruction or perforation.
• Lungs: Kaposi's sarcoma of the lungs, called pulmonary KS, can cause pneumonia (lung inflammation), either with or without skin lesions. Symptoms may include fever, chills, shortness of breath, cough, and green or bloody sputum. If not treated aggressively, respiratory failure and death are possible.
• Liver: Kaposi's sarcoma of the kidneys, called hepatic KS, affects 34% of people with HIV-associated KS. Hepatic KS can cause classic symptoms of hepatitis, including severe fatigue, nausea, vomiting, abdominal pain, clay-colored stools, and jaundice (yellowing of the skin and whites of the eyes). While some people with hepatic KS have no symptoms, those who do are at an increased risk of multi-organ failure and death.
• Heart: Kaposi sarcoma of the heart, known as cardiac KS, is an uncommon but potentially life-threatening complication. It can cause pericardial effusion (the buildup of fluid in the lining of the heart) and lead to a medical emergency known as cardiac tamponade. Symptoms include chest pain, severe shortness of breath, rapid heartbeats, palpitations, reduced urine output, and a bluish skin discoloration (due to low blood oxygen).

Complications of Classic KS

Classic KS is a less severe form of the disease that is associated with the natural decline in immune function among aging people of certain racial or ethnic origins. Males 70 and over of Jewish, Greek, and Italian descent are most predominantly affected.

Unlike HIV-associated KS, classic KS is rarely aggressive and tends to be limited to the lower legs and hands. KS lesions in the mouth or gums are also uncommon. While classic KS rarely spreads to internal organs, it has been known to occur.

Complications of Transplant-Related KS

The underlying cause of transplant-related KS is the use of immunosuppressant drugs to prevent organ transplant rejection. Transplant-related KS can occur with any solid organ transplant but is most likely to occur after a lung transplant or kidney transplant.

Transplanted-related KS tends to affect the lower limbs and will typically clear once the immunosuppressant drug is stopped or switched. In some cases, the lesions may spontaneously clear on their own.

Although it is uncommon for transplant-related KS to affect internal organs, it has been known on rare occasions to spread to the lymph nodes, lungs, or heart. If internal organs are affected, the outcomes are generally poor.

Complications of Endemic KS

Endemic Kaposi's sarcoma is mainly confined to sub-Saharan Africa and comes in two forms: one that affects children under age 10 and the other that affects men between the ages of 20 and 50.

The form affecting men typically grows slowly and causes nodules on the lower limbs that can remain stable for many years or clear spontaneously. Although some cases have been known to spread rapidly, the lesions tend to be confined to the skin and rarely affect internal organs.

The more aggressive form of endemic KS in children typically causes tumors in the lymph nodes, with or without lesions on the skin. When both the skin and internal organs are involved, the risk of death is high, usually occurring within two months.

When to See a Healthcare Provider

While the appearance of Kaposi's sarcoma in people with HIV is not an emergency per se, it does require immediate and sometimes aggressive treatment. Although KS can occur in people with intact immune systems, it is more likely than not to be a sign that your immune system is compromised.

Being immunocompromised means you are vulnerable to an array of infections (called opportunistic infections) that your body would otherwise be able to fight off. The only way to prevent these is by starting antiretroviral therapy, which suppresses and controls HIV and allows your immune system to rebuild itself and become stronger.

Even if HIV is not involved, there is no situation in which KS should not be seen as a matter of urgency. Even if it is indolent, KS is a rare form of cancer that needs to be evaluated to determine the underlying cause.

Kaposi sarcoma is always a big deal.

Summary

Kaposi's sarcoma (KS) is a rare form of cancer that is mainly seen in people living with advanced HIV infection. The defining feature of KS is painless, purplish tumors that develop on the skin and in the mouth.

In some cases, KS can affect internal organs like the lymph nodes, lungs, liver, intestines, and heart. These can lead to an array of potentially severe and even life-threatening complications.

There are other forms of KS that affect people without HIV. Many of these are slow-growing and some may even spontaneously clear on their own without treatment. Others, like an aggressive form of KS affecting African children, are associated with a high risk of death.

A Word From Verywell

Many people regard Kaposi's sarcoma as a relic of the AIDS epidemic of the 1980s and 1990s, but it still occurs today, even among people on antiretroviral therapy.

According to a 2021 study in the journal Cancer, more and more people on antiretroviral therapy are developing KS even when their viral loads are fully undetectable, indicating that the virus is fully under control.

What the researchers found was that, even with effective HIV treatment, people are still vulnerable to KS if their immune systems are not approaching normal levels (as measured by the CD4 count). Delaying treatment until the CD4 count is low makes it more difficult to rebuild the immune system to a "safe" level. Some people who start late never do.

So, if you are at risk of HIV and do not know your status, talk to your healthcare provider about getting an HIV test. Even if you test positive for the virus, early treatment can better ensure that you live a long, healthy, disease-free life.