Small cell and follicular lymphomas typically have a chronic course with an average survival of 6 to 12 years. In the more aggressive lymphomas, the normal appearance of the lymph node is lost by diffuse involvement of tumor cells , which are usually moderate-sized or large.
A variety of systems have been used to classify NHL sub-types according to their microscopic appearance and the behavior of the disease. The Rappaport classification is an older scheme still commonly used. More recently, an international group of pathologists and clinicians developed a Working Formulation to establish a common terminology. This defined 10 major sub-types categorized as low-, intermediate- or
high-grade. These terms relate to the relative malignant potential characterized by a growth rate
that may be low (slow), high (rapid) or intermediate (moderately rapid).
How It Spreads Since lymphocytes normally travel throughout the body via the blood and the lymphatic system , malignant lymphomas can either start in or spread to virtually any organ.
A lymphoma may arise in a single lymph node or organ and stay there even when a large mass is present, or many different sites may be involved at the time of diagnosis. Low-grade lymphomas most often involve lymph nodes , bone marrow and the spleen when they are diagnosed. Intermediate- and high-grade lymphomas are most commonly found in lymph nodes, but about one-third of cases primarily involve organs separate from lymph nodes and are called extranodal.
