What is Oral Kaposi's Sarcoma?
Oral Kaposi's sarcoma is a type of Kaposi's sarcoma occurring in the mouth. Kaposi's sarcoma itself is a subtype of sarcoma, a type of cancer arising from the connective tissues, including bones, fat, tendons and endothelial tissues. Kaposi's sarcoma arises by a malignant transformation (cell mutating and turning cancerous) of the vascular endothelium, which are the cells lining blood and lymphatic vessels on the inside.
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Kaposi's sarcoma occurs commonly in patients that have a compromised immune system. It is also associated with HIV infection, as well as infection by human herpesvirus 8, also known as Kaposi's sarcoma-associated herpesvirus (KSHV) [1].
While this blog focuses on Kaposi's sarcoma in the mouth, we wrote another blog detailing the similarities and differences between Kaposi's sarcoma and bacillary angiomatosis, two conditions with similar presentations, please give that a read after this one!
Signs and Symptoms of Oral Kaposi's Sarcoma
Oral Kaposi's sarcoma (OKS) presents most commonly with lesions in the mouth, which are red, purple or brown in colour, and are either flat or raised [2]. These lesions occur primarily on the palate, but can develop elsewhere in the mouth, and can also be not pigmented (therefore have the colour of the rest of the palate) [3, 4]. In some instances, this may be the only presentation of OKS, particularly in HIV patients. Therefore, the occurrence of these lesions may be an early indicator of HIV infection [5].
In addition to the lesions, patients can also experience other oral symptoms such as candidiasis (yeast infection in the mouth), feeling of dry mouth (xerostomia), hairy leukoplasia (presence of white patches on the tongue or elsewhere), gingivitis (inflammation of the gums) and inflammation of the soft tissues surrounding the teeth (periodontitis) [6]. In rare cases, if the nasal mucosa are involved, the patient may experience a feeling of a foreign body in the throat [7].
Additionally, OKS can present with nonspecific symptoms such as unexplained fever, fatigue and malaise, diarrhoea and loss of appetite.
It is important to note that these symptoms may come and go, or vary in severity in time [1]. It is very important to consult all suspicious lesions in the mouth with a medical professional.
How is Oral Kaposi's Sarcoma Diagnosed?
OKS is diagnosed through a combination of a clinical examination, histopathology and molecular (genetic) testing.
During the clinical examination, a doctor will examine the characteristic lesions. In most cases, a biopsy of the lesion will be taken (the area will be numbed with local anaesthetic and a small sample will be taken), and examined by a pathologist under the microscope.
The most common histological finding in OKS is presence of abnormal vasculature (blood vessels), as well as extravasated red blood cells .
Haemosiderin, an iron storage molecule can also be present in the lesion, as it is one of the products of breakdown of haemoglobin, the iron-based complex that binds oxygen to red blood cells. Some lesions also contain spindle cells, a type of sarcoma cell that appears elongated with a nucleus in the middle. Additionally, some immune system infiltrate is often present, including eosinophils, macrophages, monocytes and lymphocytes [3].
Based on these histopathological features, the OKS lesions can be classified into seven categories: solid, lymphangioma-like, telangiectatic, desmoplastic, lymphangiectatic, ecchymotic, and anaplastic [8].
Additionally, molecular testing plays a role in the definitive diagnosis of OKS. The most common genetic test is detection of DNA of the human herpesvirus 8, which is one of the primary drivers of OKS [9, 10].
How is Oral Kaposi's Sarcoma Treated?
OKS is a therapeutic challenge with many variables, including the extent of the disease and the patient's overall health status and immune system function [11]. Therefore, the treatment of OKS is highly personalised.
For early-stage disease, which is usually localised to a single lesion, cryotherapy (freezing the lesion with liquid nitrogen) may be used, as well as intralesional chemotherapy (where chemotherapy drugs are injected directly to the lesion).
This is associated with less adverse effects than systemic (intravenous) chemotherapy, and is feasible in OKS due to the fact that the lesions are easily accessible in the mouth. Drugs of choice for local therapy are alitretinoin, vincristine, vinblastine and bleomycin, and Sodium Tetradecyl Sulfate (STS) [12]. In some cases, radiotherapy to the lesion may be used [13].
In HIV-infected patients, highly active antiretroviral therapy (HAART) is an important component of the therapeutic pathway, either alone or in combination with systemic therapy for OKS. This helps alleviate the HIV burden, and partially restore the immune system function [13].
In the case of more advanced disease, systemic chemotherapy is needed. Drugs of choice include pegylated liposomal doxorubicin (PLD) and daunorubicin citrate liposome (DNX), the combined treatment adriamycin-bleomycin-vincristine (ABV) and bleomycin-vincristine (BV). Paclitaxel or Interferon-alfa are also used [12].
Some non-conventional, experimental options include use of antiangiogenesis agents, which are drugs that inhibit the formation of blood vessels. This has promising results, as abnormal vasculature appears in OKS. The investigated compounds include TNP-470, thalidomide, and retinoids [11, 14].
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What is the Prognosis of Oral Kaposi's Sarcoma?
The prognosis of OKS largely depends on other factors, mainly including the immune system functionality of the patient, HIV status, as well as involvement of the disease. The survival rate varies, however some studies report an average survival time of 1 year and 9 months [15].
CD4+ cell count, a general marker of immune system function, is a good marker of OKS prognosis. A higher CD4+ count improves the prognosis, especially in combination with a low viral load in HIV positive patients. Consequently, low CD4+ count, especially with lymphedema (swelling of the lymphatic vessels) leads to poor prognosis [16].>
The therapeutic decisions are also an importnant factor in prognosis, however these are largely influenced by the location and size of the tumour. For localised disease, treatment with radiotherapy to the lesion, or injection of vinblastine to the lesion led to regression in 80% of the tumours in a study [6]. However, it's important to note that the prognosis can vary greatly among individuals, and it's crucial for patients to discuss their specific circumstances with their healthcare provider. As with every other cancer, early detection is extremely important.
