Follicular Lymphoma (FL)
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Based on the current guidelines and the current state of research, there are different diagnostic recommendations for patients with follicular lymphoma. We have summarized the most important information on classification and diagnostic methods for MLL. In addition, we provide further links on the prognosis and therapy of follicular lymphoma, so that you can inform yourself in more detail.
Follicular Lymphoma: Classification
According to the WHO 2022 classification, follicular lymphoma is a mature B-cell neoplasm and accounts for 10-20% of all lymphomas, with the highest rates reported in Western Europe and the United States and the lowest in Eastern Europe and Asia. It arises from the B cells of the germinal center of the lymphoid follicle (centrocytes & centroblasts). Currently, the following variant forms are distinguished (WHO 2022):
Table 1: Follicular Lymphoma WHO classification (WHO 2022)
Variant forms of follicular lymphoma |
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Classic FL (cFL) |
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IGH::BCL2/t(14;18) positive |
Follicular large B-cell lymphoma (FLBL) |
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Largely equals FL grade 3B |
FL with uncommon features (uFL) |
FL with blastoid/large centrocytes |
Variant immunophenotypic and genotypic characteristics, inferior survival, need to be distinguished from LBCL-IRF4 |
FL with diffuse growth pattern |
Associated with CD23 expression, absence of BCL2 translocation, frequent STAT6 mutations along with 1p36 deletion or TNFRS14 mutation |
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In situ follicular B-cell neoplasm (ISFN) |
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Infiltration of single germinal centers with IGH::BCL2 t(14;18)-positive cells; low potential for progression |
Duodenal-type FL |
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IGH::BCL2/t(14;18) positive, mostly confined to intestinal mucosa, low risk of progression |
Paediatric-type FL |
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No BCL2 translocation |
Diffuse variant of follicular lymphoma (dFL) |
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No IGH::BCL2/t(14;18) translocation, similar expression profile as typical FL |
The WHO 2017 histologic classification of follicular lymphomas based on their centroblast content into grades 1, 2, 3A, and 3B, with grades 1-3A belonging to indolent lymphomas and grade 3B to aggressive lymphomas (Swerdlow et al. 2017) is now no longer mandatory (WHO 2022). The progression of lymphoma is assessed using the Ann Arbor classification. The grading here is into stages I-IV (Onkopedia guideline follicular lymphoma 2023).
Follicular Lymphoma: Diagnostic methods
Follicular Lymphoma: Prognosis
The Follicular Lymphoma International Prognostic Index (FLIPI) and the genetically enhanced m7-FLIPI are used for risk assessment of follicular lymphoma (Solal-Celigny et al. 2004, Pastore et al. 2015).
Follicular Lymphoma: Recommendation
Important notes on the examination material
The diagnosis of follicular lymphoma should be made on the basis of surgical lymph node extirpation, if possible, and also from peripheral blood and bone marrow in advance or in parallel. For initial screening in inaccessible, e.g. retroperitoneal lymph nodes, a lymph node biopsy can be performed alternatively. Fine-needle aspiration (cytology) alone is not sufficient because of possible focal heterogeneity of lymphoma tissue and the possible need for further immunologic and molecular genetic testing.
If lymphoma cells are detected in peripheral blood, the diagnosis can initially be made with a high degree of confidence without bone marrow biopsy or lymph node sampling. If enlarged lymph nodes are clinically prominent, a lymph node should be removed and histologically and immunohistologically processed. Based on these findings, an extended material sampling, e.g. of bone marrow, is then useful in individual cases and if clinically relevant.
Follicular Lymphoma: Therapy
Reviews of treatment strategies are available in the Onkopedia Follicular Lymphoma Guideline, from Jacobsen (Jacobsen 2022) and from Gordon et al. (Gordon et al. 2023).
Status: May 2024