Non-Hodgkin's Lymphoma - Introduction

B-cell Lymphomas Classified by Grade

Indolent (Slow-Growing) Lymphomas (also referred to as Low-Grade Lymphomas)

Follicular lymphomas (FLs). Follicular small cleaved cell lymphoma (grade I) and follicular mixed small and large cell lymphoma (grade II). FLs account for 70% of indolent tumors and 20% of all NHLs in industrialized countries. It is very rare in developing countries and in Asia.

Lymphoplasmacytoid/Waldenstrom's macroglobulinemia. Often found in bone marrow, lymph nodes, and spleen. Can cause blood to become viscous and "sticky."

Marginal zone lymphomas (MZL). MZLs often occur as a result of a pre-existing disorder such as hepatitis C, bacterial infection in the stomach (H. pylori ), or an autoimmune disorder (Sjögren syndrome in the salivary glands or Hashimoto's thyroiditis in the thyroid gland). They may be classified as:

• Monocytoid B-cell lymphoma, which involves only lymph nodes
• Splenic marginal zone lymphoma, which affects the spleen, blood, and bone marrow
• Mucosa-associated lymphoid tissue (MALT) lymphoma, which usually involves the gastrointestinal tract, thyroid, lung, breast, or skin

There is some controversy over whether MALT is a variation of MZL or a completely separate type of lymphoma that is more suitably classified as a separate low-grade lymphoma. At this time, it is classified as an MZL.

Aggressive Lymphomas (also referred to as Intermediate- and High-Grade Lymphomas)

Diffuse large-cell lymphomas (DL). DLs are the most common NHLs, accounting for about 40% of all cases. Subtypes include the following:

• Primary mediastinal large B-cell lymphoma
• Follicular large cell lymphoma
• Anaplastic large cell lymphoma
• T-cell lymphomas (not covered in this report)

In about 40% of cases, these DL lymphomas appear in areas outside lymph nodes, including digestive tract, skin, bone, thyroid, and testes.

Burkitt's lymphoma/diffuse, small noncleaved cell lymphoma. This is the most common childhood NHL. In African children, it often involves facial bones and is associated with Epstein-Barr infection.

Mantle cell lymphoma. Mantle cell lymphomas are found in lymph nodes, the spleen, bone marrow, blood, and sometimes the gastrointestinal system (lymphomatous polyposis). This lymphoma is similar to indolent lymphomas at the time of diagnosis, but it is more aggressive.

Lymphoblastic lymphoma. This lymphoma often occurs in young people. It is associated with a large mediastinal mass (occurring in chest cavity between the lungs) and carries a high risk for spreading to bone marrow and central nervous system.