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Chapter 61: Diffuse Large B-Cell Lymphoma

DEFINITION

  • Diffuse large B-cell lymphomas (DLBCLs) are a heterogeneous group of aggressive lymphomas of large, transformed B cells.

  • DLBCLs can arise de novo or may transform from a low-grade lymphoma, such as small lymphocytic lymphoma or follicular lymphoma.

  • Table 61–1 lists the variants and subtypes of DLBCL.

TABLE 61–1DIFFUSE LARGE B-CELL LYMPHOMA: VARIANTS AND SUBTYPES
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TABLE 61–1 DIFFUSE LARGE B-CELL LYMPHOMA: VARIANTS AND SUBTYPES

  1. Diffuse large B-cell lymphoma, not otherwise specified (NOS)

    1. Common morphologic variants

      1. Centroblastic

      2. Immunoblastic

      3. Anaplastic

    2. Rare morphologic variants

    3. Molecular subgroups

      1. Germinal center B-cell–like

      2. Activated B-cell–like

    4. Immunohistochemical subgroups

      1. CD5-positive DLBCL

      2. Germinal center B-cell–like

      3. Nongerminal center B-cell–like

  2. Diffuse large B-cell lymphoma subtypes

    1. T-cell/histiocyte-rich large B-cell lymphoma

    2. Primary DLBCL of the CNS

    3. Primary cutaneous DLBCL, leg type

    4. EBV-positive DLBCL of the elderly

  3. Other lymphomas of large B cells

    1. Primary mediastinal (thymic) large B-cell lymphoma

    2. Intravascular large B-cell lymphoma

    3. DLBCL associated with chronic inflammation

    4. Lymphomatoid granulomatosis

    5. ALK-positive DLBCL

    6. Plasmablastic lymphoma

    7. Large B-cell lymphoma arising in HHV8-associated multicentric Castleman disease

    8. Primary effusion lymphoma

  4. Borderline cases

    1. B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma

    2. B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and classic Hodgkin lymphoma

ALK, anaplastic lymphoma kinase; DLBCL, diffuse large B-cell lymphoma; EBV, Epstein-Barr virus; HHV, human herpes virus.

Source: Williams Hematology, 8th ed, Chap. 100, Table 100–1, p. 1548.

EPIDEMIOLOGY

  • Most common B-cell lymphoid neoplasm in the United States and Europe and accounts for approximately 28 percent of all mature B-cell lymphomas.

  • The most common presentation is in late middle-aged and older persons.

  • Median age at diagnosis is approximately 65 years.

ETIOLOGY AND PATHOGENESIS

  • Molecularly heterogeneous disease with multiple complex chromosomal translocations and genetic abnormalities as identified by cytogenetics and gene expression profiling.

  • Disease is derived from B cells that have undergone somatic mutation in the immunoglobulin (Ig) genes.

  • BCL6 gene rearrangements may be specific for DLBCL.

    — Approximately 40 percent of cases in immunocompetent persons and approximately 20 percent of HIV-related cases display BCL6 rearrangements.

    — BCL6 protein mediates the specific binding of several transcription factors to DNA.

  • Approximately 30 percent of patients have the t(14;18) translocation involving BCL2 and the Ig-heavy-chain gene.

    — The presence of p53 mutation in combination with BCL2 denotes that the tumor is derived from a transformation of a prior follicular lymphoma.

  • Aberrant somatic mutation occurs in more than 50 percent of cases and targets multiple loci (e.g., IGH, PIM1, MYC, RhoH/TTF (ARHH), PAX5, c-MYC).

  • Three molecular subtypes have been identified determined by gene expression profiling:

    — Germinal center B-like (GCB): arise from normal germinal center B cells.

    — Activated B-cell-like (ABC): may arise from postgerminal center B cells that are arrested during plasmacytic differentiation.

    — Primary mediastinal B-cell lymphoma: might arise from thymic B cells.

CLINICAL FEATURES

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