The Origin, Symptoms, and Treatment of Kaposi Sarcoma

There are four variants of Kaposi sarcoma, and all have completely different prognoses. They all have one thing in common, however, and that is that they're all caused by the VHH-8 virus.
The Origin, Symptoms, and Treatment of Kaposi Sarcoma

Last update: 13 July, 2021

Kaposi sarcoma (KS) is a malignant antiproliferative tumor that forms in the lining of a person’s blood and lymphatic vessels. It’s associated with human herpesvirus type 8 (HHV-8) infection and there are four variants: classical, endemic, HIV-associated, and immunosuppression-linked.

The manifestation is clearly male-biased (it affects 17 males for every female) and occurs primarily in patients over 50 years of age with an Eastern or Mediterranean family lineage. The prevalence of the disease correlates positively with peaks in HHV-8 infection worldwide.

The USA estimates that 1 in 100,000 people experience it and this value has remained stable since 1997. Meanwhile, in the past, the severity of this condition was significant in areas of Tanzania and Cameroon, with an incidence of more than six cases per 1000 people.

What’s Kaposi sarcoma?

As indicated by the HHS Public Access portal, Kaposi sarcoma is a malignant neoplasm of endothelial cells with a clear inflammatory component and heterogeneous histopathology. Simply put, there’s an excessive proliferation of the cell bodies of the endothelium, the tissue lining the vascular channels of the body.

The cancer cells in this type of neoplasm adopt a spindle shape so they’re known as spindle cells. The proliferation of these bodies results from the stimulation of cytokines, secreted in response to infection by the HHV-8 virus, a pathogen with a double DNA strand.

The VHH-8 virus has about 165,000 base pairs in its genome, so it’s complex. Upon infection, the virus enters the lymphocytes (white blood cells) and begins replication in two specific phases: lytic and latent. As a result, it can go unnoticed even though it causes persistent infections.

We’re not going to dwell on the mechanism by which the virus turns into cancer and it might be enough to know it’s conducive to it. According to the Medigraphic portal, this pathogen has genes that are homologous to proto-oncogenes in its DNA — involved in the development of tumors.

The stages of Kaposi sarcoma

There are three stages in the development of Kaposi sarcoma:

  • The main characteristic of the patch stage is the production of irregular spindle cells in the affected endothelium. In addition, blood vessels grow around the dermal area. It’s for this reason that Kaposi tumors have a characteristic red color.
  • The plaque stage is that in which the blood vessels continue to proliferate, surrounding other pre-existing ducts. Furthermore, there are extravasated red blood cells, macrophages, and rare hyaline globules.
  • The nodular form is a well-circumscribed cancerous nodule easily visible in the dermis.

In short, this is a highly vascularized tumor. Many atypical blood vessels develop, resulting in the extravasation of red blood cells and giving the mass a purplish color. In addition, the body’s inflammatory response promotes redness and pain in the area.

A group of blood platelets.
The endothelium is a lining inside the blood vessels and serves as a seat for tumor initiation.

Types of Kaposi sarcoma and their symptoms

As if the histologic complexity of the tumor wasn’t enough, note that Kaposi sarcoma can manifest in several forms. The Actas Dermo-Sifiliográficas journal lists the particularities of each one as follows.

Classic form

This is a rare tumor that affects males of Mediterranean or Central European descent. It usually appears on the soles of the feet, as patches with a reddish and violaceous form that develop to the stage of plaques and nodules.

It’s a chronic, non-painful condition that affects 0.18-13.2 cases per 10 000 000 population. Moreover, it’s painless and chronic but 2% of patients die from the spread of cancerous lesions.

Endemic form

As mentioned above, Africa has the worse scenario as far as HHV-8 is concerned. Seropositivity for the virus ranges from 2 % (in Eritrea, for example) to almost 100 % in Central Africa. Because of these alarming figures, Kaposi’s sarcoma is the most common type of tumor in men in Uganda and Zimbabwe.

It usually afflicts young adults and teenagers. There are two varieties in the endemic form: a rather aggressive one involving the patient’s lymph nodes (in children) and another with vascularized nodules in the extremities (in adults).

HIV-associated form

HIV-infected patients who don’t properly take antiretroviral medications (ART) are at risk for this variant. It’s the type of cancer most associated with them and its manifestation is much more severe than the classical form. Also, this neoplasm is diffuse and involves the internal organs.

Unfortunately, the estimated survival in these patients is approximately 69% and up to 25% of HIV-positive patients had Kaposi sarcoma in the past.

Iatrogenic Kaposi sarcoma

As per the MSD Manual, this form develops several years after an organ transplant. It usually appears when a patient gets an infected organ transplant. The risk in these people is 150 to 200 times higher than in the general population.

Causes

HHV-8 appears in practically 100% of lesions characterized as Kaposi sarcoma, be it classical, endemic, HIV-associated or iatrogenic. In any case, people with AIDS are much more likely to experience it, according to the Mayo Clinic.

This virus is typically transmitted beyond epidemiological risks. The most common vehicle is saliva, although a person can pass it to another via an organ transplant or a blood transfusion. Having multiple sexual partners is often conducive to the onset of this disease.

How can it be diagnosed?

According to the U.S. National Library of Medicine, it all starts with a physical examination of the patient, with special emphasis on swellings.

As mentioned above, these appear as painless plaques or nodules on the legs, soles of the feet, or face. They’re vascularized, so their color is reddish-purple.

Beyond these signs, it’s necessary to do certain tests on a person suspected of having the condition. Among them:

  • A bronchoscopy consists of a thin tube introduced through the mouth or nose to obtain images of the upper airways. Doctors also take samples (biopsies) from the areas of tissue that seem abnormal.
  • A colonoscopy follows the same premise but is for looking at the superficial tissue of the rectum and colon.
  • A chest X-ray can detect the spread of Kaposi’s sarcoma into the patient’s lung tissue.
  • Skin biopsy. As mentioned above, most tumors first appear on the skin, either on the soles of the feet or in the mouth. 30% of Kaposi’s sarcomas are oral, so a doctor must do a biopsy and analyze it under the microscope.

In general, the diagnosis of a typical sarcoma can be carried out with a mere sample of the affected area. On the other hand, HIV patients require a thorough examination.

A person with oral cancer.
Oral manifestation of Kaposi sarcoma is common so anyone who suspects it must consider an examination and biopsy of the area.

Learn about Sarcoma: Characteristics and Causes

Treatment of Kaposi sarcoma

A skin sarcoma usually requires local surgery and liquid nitrogen in vincristine injections, also used for acute leukemia. Chemotherapy is the long-term approach for endemic and systemic forms, especially in children.

In addition, people with HIV-associated sarcoma respond well to highly active antiretroviral therapy (HAART). It can either cause regression or lead to the complete disappearance of the tumor in the most optimistic scenarios. Doctors use a combination of HAART and chemotherapy in the most severe cases.

Final outlook

Approximately 10-20% of patients with classic Kaposi sarcoma die from the viral disease, but a lesser percentage will also develop secondary malignant lesions. These are often lethal.

According to the AECC, the overall survival rate five years after diagnosis is 74%, reaching 81% in more localized cases. Cutaneous involvement is the least serious (nine out of 10 survive the first year), but when it spreads to the viscera it worsens (seven out of 10).

Patients with HIV have the worst prognosis and estimated survival of 69%. In any case, it depends on the extent of the sarcoma.

HHV-8 is always behind it

The term “Kaposi sarcoma” encompasses a heterogeneous group of conditions. As you read above, the classic variants have little to do with a disseminated one related to HIV.

In any case, the causative agent is always the same: infection by the HHV-8 virus. The prevalence varies according to region, although Africa is the most affected.

In short, we’re dealing with a varied condition in which the prognosis depends on the patient’s situation. However, there’s not much one can do to prevent infection.

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