What is it?
Lymphomas are cancers of the lymphoid cells, a particular type of white blood cell which fight infection and monitor the immune system. Lymphomas form solid tumours found in lymph nodes and all other parts of the body. Lymph nodes are commonly involved because this is the part of the body where lymphocytes carry out their main functions. Lymphoma is distinguished from leukaemia by the lymphoid cells of leukaemia which are easily found in the peripheral blood whereas this occurs rarely and usually only in very advanced stages of lymphoma.
Lymphoma is not a single disease but rather a number of diseases grouped together because of the abnormality in the lymphoid cell and how patients present when they have these diseases. Over the centuries, these diseases have been described and re-described, grouped in one way and then another, leading to confusion and contradictory naming conventions.
The current convention is to categorise each lymphoma by its lymphoid cell type through a series of diagnostic tests. These are grouped under the main umbrella lymphoid neoplasms. Lymphoid neoplasms are then divided into three major categories, Mature B-cell neoplasms, Mature NK-cell/T-cell neoplasms and Hodgkin lymphoma. Figure 1 below shows the current classification. Although the category non Hodgkin lymphoma is not part of the current classification system, the term still remains in frequent use and has been included in the diagram for clarity.
Figure 1: Classification of lymphomas