Kaposi Sarcoma: Understanding This Vascular Skin Tumor

The Bottom Line

Kaposi sarcoma (KS) is a type of cancer that grows from the cells lining blood and lymph vessels, causing purple or brown spots, patches, and bumps on the skin. It is caused by a virus called KSHV (human herpesvirus 8) and almost always develops in people whose immune system is weakened—whether from HIV, organ transplant medications, or other causes. With modern treatment, including HIV medications and targeted chemotherapy, many people with KS achieve significant improvement and can live for years with the condition well controlled.

What Is Kaposi Sarcoma?

Kaposi sarcoma is a cancer that starts in the cells that line your blood and lymph vessels. These abnormal cells form lesions that appear as flat spots (macules), raised patches (plaques), or nodules (bumps) that range in color from pink to red to purple to dark brown. The color comes from the abnormal blood vessels packed within each lesion.

KS is caused by a virus called Kaposi sarcoma-associated herpesvirus—also known as human herpesvirus 8, or KSHV/HHV-8. The virus alone rarely causes KS. Instead, it typically develops when the immune system is too weakened to keep the virus in check. This is why KS is strongly associated with:

  • HIV infection and AIDS (the most common setting in the United States)
  • Organ transplantation and the immunosuppressive drugs required to prevent rejection
  • Advanced age in certain populations (classic KS)

KS is classified differently from most skin cancers. It is not caused by sun damage or UV radiation. Understanding which type of KS you have is important because it shapes your treatment options.

The Four Types of Kaposi Sarcoma

1. Classic KS

This form occurs mainly in older men of Mediterranean or Eastern European ancestry. It tends to be slow-growing, affecting the skin of the lower legs and feet. Oral involvement occurs in 10-30% of cases. Visceral (internal organ) involvement is less common than in AIDS-associated KS. Median survival from diagnosis is 10-15 years.

2. Endemic (African) KS

This form affects younger people in sub-Saharan Africa, sometimes including children. It can be more aggressive than classic KS, particularly in younger patients.

3. Transplant-Associated (Iatrogenic) KS

This form develops in organ transplant recipients taking immunosuppressive medications. The incidence is 300-500 times higher than in the general population. Reducing or changing immunosuppressive medications—when medically safe—often leads to significant improvement.

4. AIDS-Associated (Epidemic) KS

This is the most common form in the United States, developing in people with HIV whose immune system has been severely weakened (particularly when the CD4 count falls below 200 cells per microliter). At CD4 counts below 50, the risk of developing KS approaches 40%. With effective antiretroviral therapy (ART) raising CD4 counts, this risk drops to 5-10%. The widespread use of ART has dramatically reduced AIDS-associated KS rates since the 1990s.

What Does Kaposi Sarcoma Look Like?

KS lesions have a characteristic appearance that usually makes them recognizable:

  • Color: Violaceous (purple), dark red, brown, or pink. The color reflects the abnormal blood vessels within each lesion.
  • Shape: Start as flat spots (macules) and may progress to raised plaques or nodular (bumpy) lesions over time
  • Location: Classic KS typically starts on the lower legs and feet. AIDS-associated KS often appears more widely distributed, including on the face, mouth, and trunk
  • Pain: Individual skin lesions are usually painless, though extensive lesions or those causing swelling can become uncomfortable

In AIDS-associated KS, about 20-50% of patients also develop oral lesions, particularly on the palate (roof of the mouth). Pulmonary (lung) and gastrointestinal involvement indicates more advanced disease and requires urgent attention.

How Is Kaposi Sarcoma Diagnosed?

Your doctor will likely suspect KS based on the appearance of the lesions, especially in the context of immune suppression. Diagnosis is confirmed with a skin biopsy—a small sample of the lesion is removed and examined under a microscope. The pathologist looks for:

  • Spindle-shaped cells proliferating within the lesion
  • Slit-like spaces resembling abnormal blood vessels
  • Positive staining for KSHV/HHV-8 proteins (immunohistochemistry)

Once KS is confirmed, your doctor will evaluate for internal involvement with imaging (CT scan, endoscopy if bowel symptoms are present, or bronchoscopy if lung symptoms occur). In HIV-related KS, your CD4 count and viral load are central to understanding prognosis and guiding treatment.

Treatment Options

Treatment for KS depends on the type of KS, the extent of disease (how many lesions, whether internal organs are involved), and your overall immune status.

For AIDS-Associated KS: Antiretroviral Therapy First

The most important first step is optimizing HIV treatment. Starting or intensifying antiretroviral therapy (ART) raises your CD4 count, restores immune function, and allows your immune system to fight the virus driving KS. About 40-50% of AIDS-associated KS patients experience significant KS improvement from ART alone within 3 months—without any specific anti-cancer drug. ART is always the cornerstone of treatment, with additional chemotherapy reserved for patients whose KS progresses despite good immune recovery.

For Transplant-Associated KS: Reducing Immunosuppression

When medically safe, reducing or switching the medications that suppress your immune system can trigger KS remission. This decision is made carefully in consultation with your transplant team, balancing KS control against the risk of organ rejection.

Local Treatments (for limited disease)

  • Intralesional chemotherapy: Injecting vinblastine or interferon directly into individual lesions. Response rates of 40-60% for treated spots with minimal whole-body side effects.
  • Topical alitretinoin gel: A prescription retinoid gel applied directly to lesions. Achieves response in 40-50% of lesions in suitable patients.
  • Radiation therapy: Effective for localized skin lesions, particularly on the face or feet. Provides good local control.
  • Cryotherapy or laser: For small, isolated cosmetic lesions.

Systemic Chemotherapy (for widespread or internal disease)

  • Liposomal doxorubicin (Doxil): The most commonly used systemic treatment. Given by IV infusion every 3 weeks. Response rates of 50-60% in AIDS-associated KS. Average progression-free survival is 6-8 months. It has less heart toxicity than standard doxorubicin because of its special formulation.
  • Paclitaxel (Taxol): An alternative for patients who don't respond to doxorubicin. Given every 2 weeks by IV. Response rates of 40-50%. Main side effect is peripheral neuropathy (numbness/tingling in hands and feet) with prolonged use.

What Can You Expect Long-Term?

The outlook for KS has improved dramatically since the development of effective ART for HIV. Key points:

  • Classic KS: very slow-growing, median survival 10-15 years from diagnosis
  • AIDS-associated KS with optimized ART: median survival 2-5 years; patients who achieve CD4 counts above 200 have much better outcomes
  • Transplant-associated KS with immunosuppression reduction: many patients achieve durable remission
  • Pulmonary (lung) KS without treatment carries a median survival of only 3-6 months, underscoring the importance of prompt diagnosis and treatment

Complete cure is uncommon but not impossible, particularly in AIDS-associated KS where immune reconstitution through ART can produce long-lasting remissions. KS is best managed as a chronic condition—one that can be controlled effectively for many years with the right treatment.

When to See a Dermatologist

  • You have HIV and notice new purple, red, or brown spots on your skin or in your mouth
  • You are a transplant recipient and have developed new skin lesions
  • You are an older individual of Mediterranean or Eastern European ancestry with lesions on your lower legs that have not healed
  • You have been diagnosed with KS and want to understand your treatment options
  • A known KS lesion has rapidly grown, started bleeding, or new lesions have appeared
  • You are experiencing shortness of breath or coughing blood and have a known diagnosis of KS

Frequently Asked Questions

Is Kaposi sarcoma contagious?

The KS lesions themselves are not contagious and cannot spread from person to person. The underlying virus (KSHV) can be transmitted through sexual contact and saliva, similar to how other herpesviruses spread. However, the vast majority of people who become infected with KSHV never develop KS. The virus only causes KS in people who are significantly immunosuppressed. Standard precautions for contact with body fluids apply, but casual contact with someone who has KS poses no risk.

Can KS go away on its own?

In AIDS-associated KS, yes—when ART successfully restores immune function, KS lesions can shrink and even disappear without specific anti-cancer treatment. This is called immune reconstitution. Similarly, in transplant-associated KS, reducing immunosuppression can trigger spontaneous remission. In classic KS in older individuals, the disease often progresses very slowly and may remain stable for years without treatment.

Will KS affect my appearance permanently?

With treatment, many lesions shrink significantly or resolve completely. However, some treated areas may leave behind faint discoloration or slight texture changes in the skin. Lesions on the face are often the most distressing cosmetically, and targeted local treatments (radiation, intralesional therapy) can be effective for prominent facial lesions. Your dermatologist and care team can discuss cosmetically focused treatment options if appearance is a concern for you.

What is the difference between KS and a bruise or blood blister?

KS lesions can sometimes be confused with bruises or blood blisters, but there are key differences. KS lesions do not fade or resolve over 1-2 weeks the way bruises do. They are not painful when pressed. They tend to grow slowly over time rather than improving. If you have risk factors for KS (HIV, organ transplant, older age with Mediterranean ancestry) and notice persistent purple or red spots, see a dermatologist for evaluation rather than waiting.

References

  1. Bower M, Collins S, Cottrill C, et al. British HIV Association guidelines for HIV-associated malignancies 2008. HIV Med. 2008;9(6):336-388.
  2. Dezube BJ. Clinical presentation and natural history of AIDS-related Kaposi's sarcoma. Hematol Oncol Clin North Am. 1996;10(5):1023-1029.
  3. Stebbing J, Sanitt A, Nelson M, et al. A prognostic index for AIDS-associated Kaposi's sarcoma in the era of highly active antiretroviral therapy. Lancet. 2006;367(9521):1495-1502.
  4. Nasti G, Talamini R, Antinori A, et al. AIDS-related Kaposi's sarcoma: evaluation of potential new prognostic factors and assessment of the AIDS Clinical Trial Group staging system in the HAART era—the Italian Cooperative Group on AIDS and Tumors and the Italian Cohort of Patients Naive From Antiretrovirals. J Clin Oncol. 2003;21(15):2876-2882.
  5. Cattelan AM, Calabro ML, Aversa SM, et al. Regression of AIDS-related Kaposi's sarcoma following antiretroviral therapy with protease inhibitors: biological correlates of clinical outcome. Eur J Cancer. 1999;35(13):1809-1815.
  6. Northfelt DW, Dezube BJ, Thommes JA, et al. Pegylated-liposomal doxorubicin versus doxorubicin, bleomycin, and vincristine in the treatment of AIDS-related Kaposi's sarcoma. J Clin Oncol. 1998;16(7):2445-2451.

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