Doctors look at several different factors to group non-Hodgkin lymphoma (NHL).
Understanding how the different types of NHL are grouped or classified can be difficult. There are many different types of NHL. It is estimated that there are more than 60 subtypes.
Various systems for classifying lymphomas into groups have been used over the years. The latest is the World Health Organisation classification of 2016. We give a simple description of the groups in this section.
Tests at diagnosis
Your doctor finds out which type of NHL you have by removing part, or all of a lymph node, and sending it to the laboratory. This is called a biopsy. A specialist doctor (pathologist) examines it under a microscope.
The pathologist examines the cells to see:
- the grade of your NHL
- the type of cell affected (B cell or T cell)
- what the cells look like under a microscope
- which proteins (markers) are on the surface of the lymphoma cells (immunohistochemistry)
- whether there are certain gene changes in the lymphoma cells (cytogenetics)
Type of white blood cell - B cell or T cell
One way of classifying NHL is by the type of white blood cells (lymphocytes) affected. These can be B cells or T cells.
Most people with NHL have a B cell lymphoma. T cell lymphomas are more common in teenagers and young adults.
Doctors put NHL into 2 groups, depending on how quickly they are likely to grow and spread.
The 2 groups are low grade and high grade. The different grades of NHL are treated in slightly different ways.
Low grade NHL tends to grow very slowly. Doctors call them indolent lymphomas. Follicular lymphoma is the most common type of low grade lymphoma.
High grade NHL tends to grow more quickly than low grade lymphomas. Because they grow quickly your doctor might call your lymphomas an aggressive type. Diffuse large B cell lymphoma is the most common type of high grade NHL.
What the lymphoma cells look like
Different treatments are used for the different types. So knowing the type helps the doctor know how to treat them. In the laboratory a pathologist looks at the cells to see if they are:
- large or small
- grouped together in structures called follicles (follicular type) or spread out (diffuse type)
Low grade NHL tends to have small cells that are grouped together.
Remember the word diffuse can also be used to describe NHL that is widespread in the body. This is not the same as the type of NHL called diffuse large B cell lymphoma.