N o n - H o d g k i n L y m p h o m a
General
Epidemiology
• Fifth most common cause of cancer death in US!
• This year, 54,900 people in the US will receive a new diagnosis of NHL and
26,100 will die.
• Incidence and mortality have been increasing at an alarming 4% yearly since
1950.
Origin
NHL originates in a single lymph node or in lymphoid tissue; spreads to other, non-contiguous lymph nodes and organs (spleen, liver, bone marrow, others). May spill over into blood.
Immunophenotype
• 85% of cases are of B-cell immunophenotype (express CD19, 20, 22, and
surface immunoglobulin; often have immunoglobulin gene rearrangements).
• 15% of cases are of T-cell immunophenotype (express CD3, 4, 7, 8; often
have T-cell receptor gene rearrangements).
Low grade vs. high grade
Classification
Lymphomas have been through a ton of different classification schemes. It's enough to make you throw up. The classification system in use right now (and probably for the next many years) is the WHO (World Health Organization) classification. This is a nice, comprehensive list of all the lymphomas we know about at the moment. It's divided broadly into B-cell lymphomas, T-cell lymphomas, and Hodgkin lymphomas. Take a look at it (follow the link above) to get an idea of where the lymphomas we discuss fit in.
Two other lymphoma classifications are worth mentioning, because you will still see references to them from time to time. The first is the REAL (revised European-American lymphoma) classification. This classification was created in 1994, and it is really similar to the current WHO classification (it's just missing a few lymphomas that got their own special names in the WHO classification). The REAL classification was pretty cool when it came out because it took into account not just morphology (how the cells look), but immunophenotype, genetic features, and clinical features. It does not lump lymphomas together into low-, intermediate-, and high-grade groups, like the Working formulation did (see below).
The second classification you need to have heard about is the Working formulation. This classification was created in 1982 (you should have seen the mess before this one was created!). Individual lymphomas are lumped into three big categories (low-grade, intermediate-grade and high-grade) based on prognosis (low-grade=good, high-grade=bad). It was kind of cool in its day, because at least it told you how the patient might fare. It only defined lymphoma on the basis of morphology, though; it didn't take into account immunophenotype or genetic features (not much was known about that stuff way back in 1982).
