H&E Diagnosis & Classification of Lymphoma: An Overview

Lymphoma is not a single disease but a large family of cancers arising from lymphocytes — the immune cells that populate lymph nodes, bone marrow, spleen, and many other tissues. This page orients you to how a pathologist moves from a biopsy to a named diagnosis, and how the major B-cell lymphoma subtypes relate to one another. It is a navigational hub: each subtype named below links to its own detailed article. Because two major classification systems were published in 2022 and remain in simultaneous use, we flag throughout where they agree and where they diverge.

From Specimen to Diagnosis

Diagnosis begins with adequate tissue. An excisional or core biopsy of an enlarged node — or, for extranodal disease, a sample from the involved organ — is fixed, processed, and stained with hematoxylin and eosin (H&E). The H&E slide answers the first questions: Is the normal nodal architecture preserved or effaced? Are the proliferating cells small, medium, large, or mixed? Is there a follicular (nodular) pattern, a diffuse sheet, or a "starry-sky" appearance from scattered tingible-body macrophages?

H&E alone, however, rarely settles a modern lymphoma diagnosis. The defining axis of contemporary classification is entity + lineage/grade + defining genetics, not histologic pattern alone. A pathologist therefore layers on immunohistochemistry (IHC) to establish lineage and phenotype, flow cytometry to confirm clonality, and — for many aggressive entities — fluorescence in situ hybridization (FISH) and increasingly molecular sequencing. The H&E picture frames the differential; ancillary studies name the disease.

The H&E Picture (Synthesized)

Across B-cell lymphomas, a few recurring morphologic patterns recur. A follicular architecture of centrocytes and centroblasts recapitulating germinal centers suggests follicular lymphoma; the key is whether those follicles are neoplastic (BCL2-positive) or reactive. A diffuse sheet of large transformed cells effacing the node points toward diffuse large B-cell lymphoma and its high-grade relatives. Small mature lymphocytes with pale proliferation centers (pseudofollicles) characterize CLL/SLL, while monomorphic small-to-medium cells with irregular nuclei suggest mantle cell lymphoma. A starry-sky pattern with near-uniform medium cells and brisk apoptosis raises Burkitt lymphoma and its mimics. Marginal-zone (centrocyte-like) cells with lymphoepithelial lesions in an extranodal site suggest MALT lymphoma, and a spectrum of small lymphocytes, plasmacytoid cells, and plasma cells suggests lymphoplasmacytic lymphoma. These are starting points, not verdicts — morphologic overlap is precisely why immunophenotype and genetics are mandatory.

The Major Categories

Aggressive large B-cell lymphomas are anchored by [Diffuse large B-cell lymphoma, NOS (DLBCL-NOS)], the most common aggressive B-cell lymphoma. It is subclassified by cell of origin (COO) into germinal-center (GCB) versus non-GCB groups using the Hans IHC algorithm (CD10, BCL6, MUM1/IRF4) [3]. Within this family sit the high-grade entities defined by genetics: [DLBCL/HGBL with MYC and BCL2 rearrangements] (the "double-hit" category) and [High-grade B-cell lymphoma, NOS (HGBL-NOS)]. Two morphologic mimics complete the group: [Burkitt lymphoma], MYC-driven without a BCL2 translocation and with a Ki-67 approaching 100%, and [High-grade B-cell lymphoma with 11q aberration], which resembles Burkitt but lacks MYC rearrangement.

Several site-specific or biologically distinct large B-cell lymphomas are recognized separately. [Primary mediastinal large B-cell lymphoma (PMBL)] arises from thymic B-cells in young adults, shows compartmentalizing sclerosis, and carries 9p24.1/PD-L1 biology. [Primary large B-cell lymphoma of immune-privileged sites] (CNS, testis, vitreoretinal) shares MYD88/CD79B genetics. [Large B-cell lymphoma arising in immune deficiency/dysregulation] captures EBV-driven disease in transplant, iatrogenic, inborn-error, and HIV settings.

Indolent B-cell lymphomas include [Follicular lymphoma (FL)], the most common indolent type, defined by t(14;18) IGH::BCL2 and BCL2 positivity within neoplastic follicles; [Chronic lymphocytic leukemia / small lymphocytic lymphoma (CLL/SLL)] with its CD5+/CD23+/cyclin D1-negative, LEF1-positive phenotype; [Extranodal marginal zone lymphoma of MALT], often antigen-driven (e.g., H. pylori in gastric MALT); and [Lymphoplasmacytic lymphoma / Waldenström macroglobulinemia (LPL/WM)], in which MYD88 L265P is central. [Mantle cell lymphoma (MCL)], defined by cyclin D1 and t(11;14), bridges these categories — frequently behaving aggressively despite its small-cell morphology.

How Grading and Staging Work

Grading in lymphoma is entity-specific, not universal. Many entities are not graded at all: DLBCL-NOS is stratified by COO and double-hit status rather than a numeric grade, and CLL/SLL is risk-stratified by IGHV mutation status, TP53/del(17p), and cytogenetics. Where grading exists, it varies: follicular lymphoma has historically been graded 1–3A versus 3B, while mantle cell lymphoma relies on the Ki-67 proliferation index as its key prognostic measure, with blastoid and pleomorphic variants behaving worse. Staging (the anatomic extent of disease) is a separate exercise determined clinically and radiologically, distinct from the histologic classification described here.

Why Classification Matters

Getting the entity right is not academic. Classification determines prognosis and, increasingly, eligibility for specific drug classes. Double-hit status (MYC plus BCL2 rearrangement) carries adverse prognosis and influences regimen intensity — making FISH for MYC, BCL2, and BCL6 essential in large B-cell cases; the evidence suggests this is the single highest-yield distinction to get right in aggressive lymphoma [4]. PMBL's PD-L1 biology makes checkpoint blockade relevant. MYD88 L265P in LPL/WM is associated with BTK-inhibitor sensitivity, with CXCR4 status modifying response. TP53/del(17p) and IGHV status guide therapy decisions in CLL/SLL. In MALT lymphoma, t(11;18) predicts failure of antibiotic-based therapy. None of this is patient-directed advice — it illustrates why precise classification underpins rational management.

What's Current: Recent Reclassification

The 2022 publication of both the WHO 5th edition (WHO-HAEM5) [1] and the International Consensus Classification (ICC) [2] created a genuine currency problem: both are in active use and diverge on several entities. Any aggressive-lymphoma report should state which system it follows.

Key divergences to know:

• Double-hit narrowed. Both systems now restrict the double-hit category to MYC + BCL2 rearrangements; MYC/BCL6-only cases were removed and reassigned to DLBCL-NOS or HGBL-NOS [4]. The naming differs: WHO5 uses "DLBCL/HGBL-MYC/BCL2" while ICC prefers "high-grade B-cell lymphoma with MYC and BCL2 rearrangements."
• Follicular lymphoma grading. WHO5 de-emphasizes numeric 1–2–3A grading in favor of a biology-based framework (classic FL, FL with predominantly diffuse pattern, follicular large B-cell lymphoma), whereas ICC retains more traditional grading. Reconcile carefully.
• 11q entity renamed. "Burkitt-like lymphoma with 11q aberration" became HGBL/LBCL with 11q aberration, reflecting molecular data showing it is closer to DLBCL than Burkitt and is MYC-negative [5].
• Immune-privileged sites merged in WHO5 into one family (CNS, testis, vitreoretinal); ICC keeps them more separate.
• Immune deficiency/dysregulation received a unified three-part WHO5 naming scheme (clinical setting + pathology + virus); ICC organizes these differently.

Because entity names and boundaries are evolving, verify terminology against the current WHO-HAEM5 and ICC texts at the time of reading.

References

1. Alaggio R, Amador C, Anagnostopoulos I, et al. The 5th edition of the WHO Classification of Haematolymphoid Tumours: Lymphoid Neoplasms. Leukemia. 2022. doi:10.1038/s41375-022-01620-2
2. Campo E, Jaffe ES, Cook JR, et al. The International Consensus Classification of Mature Lymphoid Neoplasms. Blood. 2022. doi:10.1182/blood.2022015851
3. Hans CP, Weisenburger DD, Greiner TC, et al. Confirmation of the molecular classification of DLBCL by immunohistochemistry using a tissue microarray. Blood. 2004. doi:10.1182/blood-2003-05-1545
4. Davies AJ. The high-grade B-cell lymphomas: double hit and more. Blood. 2024. doi:10.1182/blood.2023020780
5. Wagener R, Seufert J, Raimondi F, et al. The mutational landscape of Burkitt-like lymphoma with 11q aberration is distinct from that of Burkitt lymphoma. Blood. 2019. doi:10.1182/blood-2018-07-864025