What are lymphomas?
Lymphoma is cancer of the lymphatic system, a network of lymph nodes, organs (including spleen, vascular gland and tonsils) and vehicles that help make up the immune system. There are many different types of lymphoma, and they can be divided into two categories: Hodgkin's disease (HD, English) and non-Hodgkins lymphoma (NHL in English). The biggest difference between these two is the cell type involved.
Roughly speaking, the HD is easier to treat than the NHL. It is easier to treat lymphoma at an early stage, when the cancer has not spread beyond the lymphatic system. Lymphoma that spreads or the bone marrow or the brain is more difficult to treat.
HIV-positive people are at a somewhat higher risk of developing NHL than HIV negative. The NHL can also progress (worsen) faster in HIV-positive people and can be more difficult to treat. It is unclear whether HIV-positive people are at greater risk of developing HD. However, the HD occurs in HIV-positive people and because of underlying immune suppression, can progress more quickly and be more difficult to treat.
A number of recent studies have found that fewer HIV-positive people are diagnosed with lymphoma today years before they were treated with the combination of anti-HIV drugs become available. The risk of developing one of the most serious types of lymphoma - lymphoma of the brain (primary CNS lymphoma), for example - decreases dramatically in recent years. However, some types of NHL - Burkitt lymphoma, for example - not decreased.
Lymphomas are more likely to occur in HIV-positive people under 200 T-cells; the primary CNS lymphoma is more likely to occur in people under 100 T-cells. However, there have been reports of lymphomas occurring in HIV-positive people with higher T-cell count.
While it is not known the cause of lymphoma, many researchers believe that environmental toxins - such as pesticides - can cause this form of cancer. The Epstein-Barr virus (EBV, in English) was also responsible for the development of lymphomas, especially in people with HIV.