Definition and Background
Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL) in the United States and worldwide, accounting for up to one-third of patients with newly diagnosed NHL in the United States. Although it can occur in childhood, the occurrence of DLBCL generally increases with age, and most patients are over the age of 60 at diagnosis.
Typical symptoms of DLBCL include a painless rapid swelling in the neck, underarms (also called the axillae), or groin caused by enlarged lymph nodes. Other symptoms may include night sweats, chills, unexplained fevers, and weight loss.
DLBCL is an aggressive (fast-growing) NHL that affects B-lymphocytes. Lymphocytes are one type of white blood cell. B-cells are lymphocytes that make antibodies to fight infections and are an important part of the lymphatic system. The lymphatic system is a complex, spidery network consisting of lymph nodes and thin tubes called lymph vessels or lymphatic vessels. Similar to blood vessels, lymphatic vessels branch out into all tissues of the body. While people can sometimes see some blood vessels, especially at their wrists and on the tops of their hands, the lymphatic vessels are not visible to the naked eye.
DLBCL can develop in the lymph nodes or in "extranodal sites" (areas outside the lymph nodes) such as the gastrointestinal tract, testes, thyroid, skin, breast, bone, brain, or essentially any organ of the body. It may be localized (in one spot) or generalized (spread throughout the body). Despite being an aggressive lymphoma, DLBCL is considered potentially curable.
Bone marrow (the spongy, fatty material inside large bones, such as the pelvis, vertebrae, and ribs) is involved in 11 to 27 percent of cases of DLBCL. Examinations of peripheral blood (blood that circulates in the blood vessels) have shown that about 33 percent of all patients who have bone marrow involvement also have cancerous cells in the peripheral blood.
Prevalence of DLBCL
DLBCL accounts for about 30 percent of new cases of NHL in the United States. The median age of DLBCL patients is 70. The disease occurs in children as well as adults, but it is more common in the elderly and slightly more prevalent in males than females.
Cancers of the blood are very complex, and the cause of DLBCL is not currently known. However, it can occur as the primary disease or as a secondary cancer after progression from another less aggressive lymphoma.
A number of DLBCLs have been categorized into subtypes which differ with respect to certain characteristics.
- T-cell/histiocyte-rich B-cell lymphoma
When viewed under a microscope, this form of DLBCL looks like a few scattered large and atypical B-cells in a background of many normal T cells and histiocytes, which are cells that migrate from bone marrow into tissues. Symptoms are typically similar to other subtypes of DLBCL and can include an enlarged liver or spleen. Approximately 50 percent of patients may be at an advanced stage of the disease when they are first diagnosed.
- Primary DLBCL of the central nervous system (CNS)
This refers to all DLBCLs that originate in either the brain or the eye. Patients with this subtype often present with neurological symptoms because of increased pressure on the brain, which can also result in headaches and blurred vision. Occasionally, patients who do not have this subtype may still develop secondary DLBCL of the CNS, which occurs when the lymphoma moves into the brain or spinal cord at a later time.
- Primary cutaneous DLBCL, leg type
This type of DLBCL consists of large transformed B-cells that typically appear as red or bluish-red tumors. Despite its name, the disease can involve the trunk, arms, legs, buttocks, or anywhere on the body. The skin lesions are strikingly round in appearance. These lymphomas can also spread to areas other than just the skin. This subtype almost always requires chemotherapy.
- Epstein-Barr virus (EBV)-positive DLBCL of the elderly
This form of DLBCL usually occurs in patients who are age 50 or older and test positive for EBV. Typically, the patient has no known deficiencies of their immune system and has not been diagnosed with lymphoma prior to this diagnosis.
- DLBCL not otherwise specified (NOS)
When DLBCL doesn’t fall into one of the subtypes listed above, it is classified as DLBCL not otherwise specified (NOS). A large number of diagnoses fall into this category. In western countries, about 25 to 30 percent of NHL cases diagnosed in adults are DLBCL-NOS, and this percentage is higher in developing countries. There are other ways of categorizing cases of DLBCL-NOS into molecular subgroups based on their genetic and immunophenotypic characteristics (see Genetics and Subtyping section for more information).