Diffuse Large B Cell Lymphoma is the most common haematological malignancy and has a variety of behaviours.
DLBCL 'not otherwise specified' is the most common form of DLBCL; there are numerous subtypes which are all rare and make up only a small percentage of the numbers. DLBCL, NOS accounts for a quarter of all non-Hodgkin's lymphomas in the western world. It is more frequent in the 3rd world. The disease usually occurs later in life but any age may be affected.
There are two pathways to development of DLBCL:
- A de novo pathway where the disease arises in the absence of other haematological malignancies
- A secondary form which arises from a less aggressive haematological malignancy, eg: follicular lymphoma
Exact aetiological causes are unknown. DLBCL is more common in the immunosuppressed.
Patients may present with nodal disease, extranodal disease or both; the largest group (40%) are located only in extranodal sites at diagnosis. The most common extranodal site is the GI tract but many other sites can be host to extranodal DLBCL. About 20% of patient have marrow involvement at diagnosis. Without therapy the disease is usually fatal in a matter of months with widespread dissemination.
Patients may present with a host of different symptoms depending on the tumour size. Most patients have no symptoms but instead complain of a rapidly enlarging mass; symptoms occur when the tumour encroaches on nearby structures.
Tumours are typically tan to white in colour and homogeneous in appearance. Necrosis is uncommon.
The basic microscopic appearance is of large cells, with vesicular nuclei and prominent nucleoli. The cells have no particular arrangement (hence the diffuse labelling). There are several variants on this appearance which represent the broad category represented by DLBCL:
- Centroblastic variant contains a number of centroblasts, large cells with oval and vesicular nuclei and prominent, membrane bound nucleoli
- Immunoblastic variant where most cells are immunoblasts (large cells with a central nucleolus)
- Anaplastic variant where most cells are very large and have significant nuclear pleomorphism.
There are numerous other variants which are much rarer.
DLBCL usually stains positively for the B-cell markers, such as CD19, CD20 and CD79a. Ki-67 staining is usually found in over 50% of cells. Other markers are variable.
There is a broad range of genetic defects in DLBCL. BCL2, BCL6 and MYC are commonly affected.
Staging and Prognosis
Staging is by the Ann Arbor system.
|I||Involvement of one lymph node site|
|IE||Involvement of a single extra-lymphatic site|
|II||Involvement of two or more lymph node sites, on one side of the diaphragm|
|IIE||Involvement of a single extra-lymphatic site and one or more lymph node groups, on one side of the diaphragm|
|III||Involvement of lymph nodes on both sides of the diaphragm|
|IIIE||Involvement of a single extra-lymphatic site, with nodes on both sides of the diaphragm|
|IIIS||Involvement of the spleen with nodes on both sides of the diaphragm|
|IIIE+S||Involvement of the spleen, a single extra-lymphatic site, with nodes on both sides of the diaphragm|
In addition, the International Prognostic Index (IPI) for lymphoma is used to gauge prognosis. The IPI consists of 5 unfavourable variables:
- Age over 60
- ECOG 2+
- High Stage (III/IV)
- Extranodal involvement of 2+ sites
- High serum LDH
This factors are combined to give an IPI risk group
|Risk||All patients||Patients ≤ 60|