Kaposi sarcoma is a form of cancer that develops in the lining of blood and lymph vessels. This condition leads to the formation of abnormal tissue, known as lesions, which can appear on the skin or on the surfaces of internal organs. These lesions often manifest as patches of discolored skin but can also form inside the body in places like the mouth, nose, liver, or lungs.
Causes and Associated Risk Factors
Kaposi sarcoma (KS) is linked to the human herpesvirus 8 (HHV-8), though most people with the virus do not develop KS. The virus is more likely to cause cancer in individuals with a compromised immune system. The reason for the weakened immunity determines the type of KS a person may develop.
Epidemic, or AIDS-related, KS is the most common type found in the United States. This type occurs in people who have an uncontrolled HIV infection, which weakens the immune system, creating an environment where HHV-8 can trigger cancer. Effective management of HIV with antiretroviral therapy can help control this form of KS.
Classic Kaposi sarcoma affects older men of Mediterranean, Eastern European, or Ashkenazi Jewish descent. This type is slow-growing and often confined to a few lesions on the skin of the lower legs. Individuals who develop classic KS may have a genetic predisposition that makes them more vulnerable to the HHV-8 virus.
Endemic Kaposi sarcoma is prevalent in parts of equatorial Africa. This type can affect a broader range of people, including children and women, and it sometimes follows a more aggressive course. Another type, iatrogenic or transplant-related KS, develops in individuals who have received an organ transplant. The immunosuppressant drugs required to prevent organ rejection weaken the immune system, which can allow a pre-existing HHV-8 infection to become active.
Signs and Symptoms
The most common indicators of Kaposi sarcoma are skin lesions, which can be flat patches or raised plaques and nodules. Their color varies from pink and red to purple or brown, often resembling bruises. Unlike bruises, these lesions do not hurt, itch, or change color when pressed.
These skin lesions can emerge in one or multiple areas of the body. Common locations include the legs, feet, face, genital area, and inside the mouth. When lesions develop on the legs or in the groin area, they can obstruct the flow of lymph fluid, leading to significant and uncomfortable swelling in the legs and feet, a condition known as lymphedema.
Kaposi sarcoma can also affect internal organs, leading to a different set of symptoms depending on the location. If lesions form in the gastrointestinal tract, they can cause abdominal pain, diarrhea, constipation, or blood in the stool. When the lungs are involved, a person might experience shortness of breath, a persistent cough, or may even cough up blood.
Diagnosis Process
To confirm a diagnosis of Kaposi sarcoma, the primary method is a skin biopsy. A small sample of tissue is removed from one of the skin lesions and sent to a laboratory. There, it is examined under a microscope by a pathologist to check for cancerous cells.
A thorough physical examination is also a standard part of the diagnostic process. A doctor will inspect the patient’s skin to determine the number, size, and location of the lesions. The inside of the mouth is also examined for any mucosal lesions.
If there is a suspicion that the cancer has spread to internal organs, further imaging tests may be ordered. A chest X-ray or a computed tomography (CT) scan of the chest and abdomen can help identify lesions in the lungs, liver, or digestive system. In cases where lung or gastrointestinal symptoms are present but imaging tests are inconclusive, a doctor might perform a bronchoscopy to examine the airways or an endoscopy to view the upper digestive tract.
Treatment Approaches
The treatment plan for Kaposi sarcoma is highly individualized. It depends on the KS type, the number and location of the lesions, and the patient’s immune system. The approach for a few slow-growing skin lesions will differ from the plan for widespread internal disease.
In cases of AIDS-related KS, the primary treatment is highly active antiretroviral therapy (HAART). This medication regimen controls the HIV infection and restores immune function. As the immune system grows stronger, it can control the HHV-8 virus, leading to the shrinking of KS lesions. For transplant-related KS, the first action is often to reduce or change immunosuppressive medications to allow the immune system to fight the virus.
Treatments for the cancer itself are categorized as either local or systemic. Local therapies are used when the disease is limited to a few skin lesions and include methods like cryotherapy (freezing), radiation, or surgical removal. Systemic therapies are required when the cancer is widespread or affects internal organs and include chemotherapy and immunotherapy.