Kaposi Sarcoma
Definition: Kaposi sarcoma (KS) is a rare disease of the endothelial cells of blood vessels and the lymphatic system. There are four types of Kaposi sarcoma: Classic KS, Human immunodeficiency virus (HIV)- associated KS, endemic or African KS and iatrogenic KS.
Etiology: Kaposi sarcoma herpesvirus (KSHV) or Human herpesvirus-8- 8 (HHV-8) is present in all forms of KS. HHV-8 is a double-stranded enveloped DNA virus with 6 major subtypes (A-F). HHV-8 interferes with many normal cell functions and requires co-factors that result in the decrease in CD4 cells and the development of Kaposi sarcoma. HHV-8 may be found in men who have sex with men (MSM), and heterosexuals and may be transmitted through saliva or arthropod bites. Iatrogenic KS occurs as a result of drug treatment leading to immunosuppression.
Epidemiology: Classic KS affects patients over 50 years old of Sub-Saharan African, Middle European and Mediterranean descent. It is associated with Diabetes Mellitus. The male-to-female ratio is 17:1. Prevalence in the United States is 1: 100,000, and mirrors the distribution of HHV-8. HIV- HIV-associated KS mainly affects MSM, and is the most common malignancy affecting children in Uganda and Zambia. HIV- positive MSM have a 5 to 10-fold increased risk of developing KS. Endemic KS arises in Africa and has a unique predilection for the pediatric population. The male-to-female ratio is 2:1. Iatrogenic KS has a male-to-female ratio of approximately 3:1. Over 5% of transplant patients who develop a de-novo malignancy have a 400- 500 fold increased risk of developing KS when compared to the general population.
Signs: KS presents with erythematous to violaceous macules, papules and nodules on the skin or mucous membranes. KS lesions begin small and eventually ulcerate. Early KS lesions appear as flat patches with associated lymphedema. These eventually evolve into plaques, nodules or scaly tumors. Patients with HIV- HIV-associated KS may develop lesions at any time during the illness. The aggression of KS is directly related to the degree of immunosuppression a patient is experiencing.
Symptoms: External KS lesions ulcerate and become painful. Internal KS lesions may be associated with bleeding, hematemesis, hematochezia, melena, shortness of breath, and peripheral edema.
Differentials: Interstitial granuloma annulare, spindle cell hemangioma, gasiform hemangioendothelioma, cutaneous angiosarcoma, pyogenic granuloma
Diagnosis: A biopsy shoring characteristic features of KS is required for a definitive diagnosis. Histologically, KS presents as a spindle cell vascular neoplasm with extravasated red blood cells and hyaline globules. Immunohistochemistry positivity for LANA-1 also differentiates KS from similar lesions.
Treatment: Skin involvement of KS is treated by local excision, liquid nitrogen and vincristine infections. Chemotherapy is used to treat endemic and systemic forms. HIV- HIV-associated KS is treated with Highly active antiretroviral therapy (HAART) and is combined with chemotherapy in severe cases. Iatrogenic KS treatment requires a reduction in immunosuppression to reduce levels of tumor growth-promoting proteins.
References:
1. Kaposi sarcoma | DermNet NZ. dermnetnz.org. https://dermnetnz.org/topics/kaposi-sarcoma
2. Bishop BN, Lynch DT. Kaposi Sarcoma. In: StatPearls. Treasure Island (FL): StatPearls Publishing; June 5, 2023.
3. Grabar S, Costagliola D. Epidemiology of Kaposi’s Sarcoma. Cancers (Basel). 2021;13(22):5692. Published 2021 Nov 14. doi:10.3390/cancers13225692