Infection with the human immunodeficiency virus (HIV) gradually diminishes the immune defenses. This is a result of the virus targeting a specific type of immune cell – the CD4+ T-lymphocyte. It opens up the body to a host of infections that affects various organs throughout the body. Some of these infections which are considered fairly harmless in a person with a healthy immune system can be potentially fatal in the backdrop of HIV/AIDS.
HIV infection and AIDS is associated with a host of diseases, some of which develop due to the lack of adequate protection once the immune system weakens sufficiently, while other diseases arise for as yet unknown reasons. Cancer is one of these conditions that is likely to occur in a person with HIV/AIDS. Some of these cancers are due to infections with certain agents. The reason why other cancers arise however is unclear.
Types of HIV/AIDS Cancers
These cancers in HIV can be classified as :
- AIDS-defining cancers
- non-AIDS-defining cancers
AIDS-defining illnesses are conditions that signify the onset of AIDS in a person who is HIV infected. This is the point where the immune capability is so compromised that a person develops conditions that are rarely seen with a healthy immune system. Certain cancers are therefore also considered to be AIDS-defining. This includes :
- Kaposi sarcoma
- Non-Hodgkin lymphoma (NHL)
- Invasive cervical cancer
It is important to note that these cancers can also occur in a person who is not infected with HIV. These incidence of these cancers in HIV positive people drops significantly with the use of HAART (highly active antitretroviral therapy).
Non-AIDS Defining Cancers
These cancers do not necessarily signify the onset of AIDS. It is more likely to occur in a person who is HIV-positive than in a person who is not. However, it is not specifically related to HIV/AIDS and can occur with HIV infection even when the immune system is not so severely compromised as to signify AIDS. HAART may not provide any significant change in the onset of these cancers in an HIV infected person. These non-AIDS-defining cancers include :
- Hodgkin lymphoma
- Anal cancer
- Colorectal cancer
- Liver cancer
- Lung cancer
- Oral cancer (mouth)
- Throat cancer
- Testicular cancer
- Skin cancers especially basal cell carcinoma, melanoma and squamous cell carcinoma
However, it is being argued that some of these cancers like Hodgkin lymphoma should be considered as an AIDS-defining cancer. (1)
Reasons and Causes
It is important to have a basic knowledge of cancer in general. Cancer is abnormal growth of cells. Normally the body has certain mechanisms that control the proliferation of cells and its differentiation as per the genetic structure. In cancer these mechanisms are disrupted. Cell growth is uncontrolled and the cells itself are structurally abnormal.
Cancer and Infections
One of the known reasons for why certain cancers occur in HIV/AIDS is a result of the weakening of the immune system. This makes the body more prone to infections. Some of these pathogens are easily combated by the healthy immune system and do not receive much attention without HIV infection. The most significant of these is Kaposi sarcoma which is caused by human herpesvirus 8 (HHV-8). Another AIDS-defining cancer that is associated with an infection is cervical cancer which is almost always due to the human papillomavirus (HPV).
Cancer and HIV
HIV infection and opportunistic infections have a host of effects on the body which may increase the risk of developing cancer. Although the virus specifically targets and destroys the CD4+ cells, HIV also disrupts other components of the immune system which may be the key to HIV-related cancers. It has not been ascertained as yet whether HIV itself is a cancer-causing agent which could also explain the the likelihood of cancer in HIV positive people. Other reasons which have been thought to come into play in the development of cancer with HIV infection includes :
- Impairment of the immune system in detecting cancerous cells and destroying it.
- Disturbance in the balance between proliferation and differentiation of cells.
- Problems with controlling damage or mutations in the genetic structure.
- Dysfunction and chronic B-cell stimulation.
- Disordered regulation of chemicals secreted by immune cells (cytokines) and hormones such as growth hormone (GH).
Cancer and Lifestyle
The role of lifestyle factors in the development of cancer is well known although not always well understood. This is irrespective of HIV infection. The most significant of these factors is cigarettes smoking as it exposes a person to numerous cancer-causing compounds (carcinogens) on a daily basis. These lifestyle factors are also known to increase the risk of cancer in a person living with HIV/AIDS. Some studies have indicated that a much larger proportion of people living with HIV/AIDS are smokers compared to the general population. (2)
In addition other risk factors may also need to be taken into consideration such as :
- use of illicit drugs
- excessive alcohol consumption
- multiple sexual partners
Below are some of the pictures of HIV-related cancers of the skin. It is important to remember that these cancers can also occur in a person with a healthy immune system although it is more common in HIV positive people. All images have been sourced from the Dermatology Atlas courtesy of Samuel Freire da Silva, M.D.
Kaposi Sarcoma Pictures
Basal Cell Carcinoma Pictures