Diffuse Large B-Cell Lymphoma (DLBCL)


Most cases of non-Hodgkin lymphoma (NHL) in the United States are diffuse large B-cell lymphoma (DLBCL), which accounts for approximately 24% of all new cases of NHL each year. DLBCL is an aggressive disease. Patients often present with rapidly enlarging lymph nodes and constitutional symptoms that require urgent medical care. Even though lymphadenopathy is the predominant initial symptom in most individuals, extranodal disease often occurs as well.1 For a definitive diagnosis of lymphoma, a thorough clinical and physical examination is required, in addition to laboratory testing and imaging.2

Laboratory Testing for DLBCL

Complete Blood Cell Count With Differential

All patients with a new diagnosis of DLBCL should have a complete blood cell (CBC) count with differential to assess the status of the bone marrow and immune system. In cases of bone marrow involvement, the CBC count can reveal anemia, thrombocytopenia, and/or leukopenia. In addition to cytopenias, atypical blood cells may be present. Circulating tumor cells can be noted in the peripheral blood on flow cytometry.2,3 

Comprehensive Chemistry Panel and Other Laboratory Tests

A comprehensive chemistry panel should be conducted to assess serum electrolytes, lactic dehydrogenase (LDH) and serum β2-microglobulin levels, kidney function, and liver function. Renal involvement may be present in up to 14% of patients and can cause electrolyte imbalances. When considering treatment for patients with abnormal renal function, the chemotherapy dosage may require adjustment.2,3 High LDH levels present in more than 50% of cases and predicts the likelihood of survival. Increased serum levels of both LDH and β2-microglobulin are clinically significant regarding prognosis and short-term response to treatment.2,4 In addition, lumbar puncture should be done for patients who have symptoms of or are at risk for central nervous system (CNS) involvement. B-cell lymphomas can be an AIDS-defining condition; therefore, HIV testing should be done. Furthermore, because considerable treatment-related immunosuppression is anticipated, the patient’s HIV and hepatitis status must be taken into account.2

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Imaging Techniques for DLBCL

For disease staging, positron emission tomography (PET) and computed tomography (CT) are the imaging methods of choice. 

Positron Emission Tomography Scans

Most patients with a B-cell lymphoma can benefit from PET because aggressive disease may be indicated by regions with a high standardized uptake value (SUV).2 The use of fluorodeoxyglucose (FDG) with PET can identify regions of elevated metabolic activity. Data from PET can also be helpful in determining if residual masses are scars or persistent lymphoma. 

Computed Tomography Scans

Lymphadenopathy, extranodal disease, and visceral involvement are all identified by CT of the neck, chest, abdomen, and pelvis. The information gained from these scans helps guide the staging process for DLBCL. CT scans are also used to assess chemotherapy results and guide radiation therapy.3

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Biopsy for DLBCL Confirmation

A surgical excisional biopsy is the worldwide standard for the diagnosis of lymphoma. While DLBCL is diagnosed through clinical examination and radiographic imaging findings, excisional biopsy results of the abnormally enlarged, suspicious-appearing lymph node can confirm a diagnosis.1,2,5 

Excisional biopsy allows the pathologist to examine the greatest possible amount of tissue, thereby avoiding the sampling error and false negatives that can occur with fine needle aspiration or core biopsy. This process also allows the discovery of the morphology and immunophenotype of B-cell markers that are required for a diagnosis.1,2,5 

Imaging can help to identify a minimally invasive site where tissue can be obtained for diagnostic biopsy and staging. Tissue biopsy of affected organs should be considered for patients without severe lymphadenopathy, especially as DLBCL frequently involves extranodal sites, such as the kidneys, adrenal gland, brain, bones, and other soft tissues.1,2,5 Occasionally, to establish the diagnosis, it may be necessary to examine the bone marrow or cerebrospinal fluid, pleural fluid, and ascitic fluid with the cell block technique and confirm the results by immunohistochemistry (IHC) or flow cytometry.5 

Characteristic morphologic features of DLBCL include complete effacement of the normal lymph node architecture by sheets of medium to large atypical cells that have large nucleoli and abundant cytoplasm. The cells express the pan-B-cell antigens, including CD19, CD20, CD22, CD79a, and CD45. Most cells also express surface immunoglobulin, and CD30 expression, noted in 14% of cases, indicates a good prognosis. Also, although CD5 is rarely expressed, it has a poor prognosis.1,2,5 

Immunohistochemistry Testing for DLBCL

IHC algorithms are widely used to identify the cell of origin in clinical practice. DLBCL is usually divided into subtypes of germinal center B-cell (GCB) DLBCL and non-GCB DLBCL.1 The Hans algorithm (staining in at least 30% of cells is considered a positive result) is used for cell-of-origin subtyping:

  • Germinal center B-cell (GCB) subtype: CD10+ or CD10- / BCL6+ / MUM1-;
  • Non-GCB subtype (a classification that incorporates the activated B-cell [ABC] subtype and cases that are unclassifiable by gene expression profiling [GEP]): CD10- / BCL6- or CD10- / BCL6+ / MUM1+.6 

Flow Cytometry Testing for DLBCL

Multiparameter flow cytometry (MFC) is a fast and economical approach to the diagnosis and monitoring of lymphoproliferative disease. MFC can be used to identify DLBCL cells in blood, bone marrow, and body fluids in samples from extranodal sites, in addition to dissociated lymph node samples.7 Flow cytometry is also used to identify various immunophenotypes, detect a clonal cell population, and differentiate between B- and T-cell origins.3 A population of monoclonal B cells with significant forward scatter (indicating a large size) can be seen with flow cytometry.6 

Immunophenotyping in DLBCL shows co-expression of pan-B-cell markers such as CD19, CD20, CD79a, CD45RA, and the nuclear transcription factor PAX5. Additional marker expression may be of prognostic significance. The proliferation factor Ki67 level is typically high, at a mean percentage of 65%. A shorter survival time has been linked to high Ki67 levels (>80%). The germinal center-associated marker CD10 is found in approximately 30% to 40% of individuals, and Bcl-6 in approximately 60%. In retrospective studies, Bcl-6 expression after treatment with rituximab has been linked to longer progression-free and overall survival.3 

Molecular/Cytogenetic Research on DLBCL Mutations

Cytogenetic or fluorescent in situ hybridization (FISH) studies can identify chromosomal translocations that are characteristic of DLBCL. These include t(3q27) (BCL6 rearrangement), seen in 35% of cases; t(14;18)(q32;q21) (BCL2 rearrangement), seen in 15% to 20% of cases; and t(8;14)(q24;q32) (MYC rearrangement), seen in fewer than 5% of cases. High grade B-cell lymphoma with BCL2 and MYC rearrangements confirmed by FISH are known as double hit DLBCL. Gene expression profiling can identify 2 subtypes of DLBCL, each with a different prognosis (GCB pattern and ABC pattern). In additionally, gene expression profiling can establish clonality.3,6 

Read more about DLBCL genetics

References

  1. Liu, Y, Barta, SK. Diffuse large B-cell lymphoma: 2019 update on diagnosis, risk stratification, and treatment. Am J Hematol. 2019;94:94:604-616. https://doi.org/10.1002/ajh.25460
  2. Padala SA, Kallam A. Diffuse large B cell lymphoma. StatPearls [Internet]. Updated April 28, 2022. Accessed August 6, 2022.
  3. ​​Ghandi S. Diffuse large B-cell lymphoma (DLBCL) workup. Medscape. Updated May 6, 2021. Accessed August 6, 2022. 
  4. Alfaifi A, Bahashwan S, Alsaadi M, et al. Metabolic biomarkers in B-cell lymphomas for early diagnosis and prediction, as well as their influence on prognosis and treatment. Diagnostics (Basel). 2022;12(2):394. doi:10.3390/diagnostics12020394
  5. Iftikhar R, Mir MA, Moosajee M, et al. Diagnosis and management of diffuse large B-cell lymphoma: Society of Medical Oncology, Pakistan Society of Hematology, and Pakistan Society of Clinical Oncology Practice Guideline. JCO Glob Oncol. 2021;7:1647-1658. doi:10.1200/GO.21.00320
  6. Klairmont MM, Park CY. Lymphoma & related disorders. PathologyOutlines. Updated June 2022. Accessed August 4th, 2022.​​
  7. Devin J, Kassambara A, Bruyer A, Moreaux J, Bret C. Phenotypic characterization of diffuse large B-cell lymphoma cells and prognostic impact. J Clin Med. 2019;8(7):1074. doi:10.3390/jcm8071074
  8. Susanibar-Adaniya S, Barta SK. 2021 Update on diffuse large B cell lymphoma: a review of current data and potential applications on risk stratification and management.  Am J Hematol. 2021;96(5):617-629. doi:10.1002/ajh.26151

Reviewed by Debjyoti Talukdar, MD, on 8/18/2022.

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