Over the years, doctors have used a variety of terms to classify the many different types of non-Hodgkin's lymphomas. Most often, they are grouped by how the cancer cells look under a microscope and how quickly they are likely to grow and spread. Some types spread more quickly than others.

• Aggressive lymphomas, also known as intermediate- and high-grade lymphomas, tend to grow and spread quickly and cause severe symptoms.
• Indolent lymphomas, also referred to as low-grade lymphomas, tend to grow quite slowly and cause fewer symptoms.