DLBCL is a cancer of B lymphocytes (B cells). In DLBCL, B cells stop responding to signals that usually limit the growth and reproduction of cells. This causes the B cells to become cancerous and grow much bigger than normal lymphocytes.
This subtype of lymphoma is called “diffuse large” because the abnormal cells are bigger than normal and spread widely throughout the tissue sample. DLBCL can occur in a single lymph node. This growth pattern contributes to the aggressive behaviour of DLBCL.
DLBCL affects patients of all age groups; however, the median age at diagnosis is roughly 60 years with slightly more males than females affected. Up to 50% of DLBCL patients have advanced disease (stage III or IV) at diagnosis.
DLBCL is typically an aggressive (fast-growing) lymphoma (also known as high-grade or acute). It can occur in lymph nodes (‘nodal’) or outside of the lymphatic system (‘extranodal’) in the gastrointestinal tract, testes, thyroid, skin, breast, bone, or brain. Extranodal disease usually indicates advanced stage disease.
DLBCL can present de novo (new) or as a transformation of other low-grade B cell lymphomas like follicular or chronic lymphocytic leukaemia/small lymphocytic lymphoma. The de novo DLBCL cases have better prognoses than the transformed cases. There are many subtypes of DLBCL, and a patient’s DLBCL subtype may affect their prognosis, response to treatment, and treatment options.
There is no known cause of DLBCL.
A family history of lymphoma, auto-immune disease, HIV infection, hepatitis C virus, a high body mass as a young adult and some occupational exposures have been identified as risk factors for DLBCL.
A biopsy is necessary to diagnose DLBCL. A biopsy can be performed with a special needle or through an incision. There are many types of DLBCL, so it is very important to have a big enough sample to make an accurate diagnosis under the microscope. An expert pathologic review is needed to confirm the diagnosis.
Other tests that might be performed include complete blood counts, erythrocyte sedimentation rate (ESR) that detects inflammation, metabolic panel to check liver and kidney function, testing for HIV and hepatitis B and C virus infections.
Positron emission tomography (PET) and computed tomography (CT) scans are used to determine where in the body the disease is present. This information is used to stage the lymphoma.
Doctors can also use a tool called the International Prognostic Index (IPI) to predict outcomes in patients. While IPI gives an overall idea of the risk of the disease, it does not always work perfectly and must be sensitively applied and analysed case-by-case.
Most cases of DLBCL do not fall perfectly into a defined category, and they are considered DLBCL not otherwise specified (NOS). However, these NOS cases can be grouped into molecular subtypes according to their cell of origin.
Within the large category of DLBCL NOS, two distinct molecular subtypes have been recognised. These groups of patients may have a different prognosis with treatment:
Germinal centre B cell (GCB)
Patients with GCB type DLBCL generally have better outcomes compared to patients with the non-GCB type. GCB subtype has a complete response (CR) rate of about 70% to standard therapy.
Activated B cell (ABC)
ABC DLBCL has a more aggressive clinical course and a worse prognosis when treated with standard therapy. The complete response (CR) rate with standard therapy for ABC-type DLBCL is not more than 30% with a high chance of relapse within two years following treatment, hence patients with ABC subtype may benefit from clinical trial.
Subtypes of DLBCL
| Subtype | Descriptions |
| Intravascular large B cell lymphoma (IVLBCL) | Lymphoma cells (cancer cells) circulate in the blood and block small blood vessels. It can affect small blood vessels in organs such as the brain, spinal cord, kidneys, lungs, and skin. It is rare, affecting 0.095 per million people. ILCL usually occurs in middle-aged or elderly people. ILCL may also be called intravascular lymphomatosis or malignant angioendotheliomatosis. |
| Primary cutaneous B cell lymphoma (PCBCL) | Characterised by skin lesions, mainly on the legs (in 80% of cases the lesions only appear on the legs), but in 12% of cases the disease can also arise in other parts of the body. Usually occurs in older adults in their 70s, and predominately women. |
| Primary central nervous system (CNS) lymphoma | DLBCL that forms in the brain and/or spinal cord. Primary CNS lymphoma can also start in the eye (called ocular lymphoma). It is rare, occurring in about 5% of all lymphomas. It may also be called B cell primary CNS lymphoma (PCL) and primary DLBCL of the CNS. If lymphoma develops somewhere else in the body and then spreads to the brain and/or spinal cord, it is called secondary DLBCL of the CNS. |
| Primary effusion lymphoma (PEL) | Causes an abnormal buildup of fluid (lymphoma cells are found in this fluid) in body cavities, including the space around the lungs, heart, or abdomen. Usually occurs in people who are immunosuppressed or who are HIV-positive and can sometimes occur in people who have had organ transplants. PEL is often linked with Epstein-Barr virus (EBV) or human herpes virus type 8. It is rare. PEL comprises ~4% of human immunodeficiency (HIV) related lymphomas and < 1% of non-HIV associated lymphomas. PEL may also be called body-cavity based lymphoma. |
| Primary mediastinal large B cell lymphoma (PMBCL) | Occurs in the thymus gland (small gland in centre of chest behind the breastbone) or in the centre of the chest (called the mediastinum). PMBCL is rare (about 3% of all lymphomas) and often occurs in younger people, with more females diagnosed than males. PMBCL may also be called mediastinal B-cell lymphoma. |
| T cell/histiocyte rich large B cell lymphoma | Rare subtype where large abnormal B cells are surrounded by many small T cells and histiocytes (cells that migrate from bone marrow into tissues), which may make the tumour cells difficult to see. Usually occurs in middle-aged adults or older, is often diagnosed at an advanced stage, appearing in lymph nodes, and frequently also found in the spleen, liver, and bone marrow. |
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