Testicular Lymphoma

Slide 1 · Testicular Lymphoma

Clinicopathologic diagnosis, molecular biology, and relapse patterns

Pathology lecture

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Distinguish primary testicular lymphoma from germ-cell and stromal tumors.

Recognize diffuse large B-cell lymphoma and the relevant diagnostic immunophenotype.

Explain the basis and clinical significance of immune-privileged-site biology.

Connect pathology to staging, central nervous system risk, and management.

Slide 3 · An older man with an enlarging testis

An older man presents with a newly enlarged, firm testis. A solid mass is demonstrated clinically.

Hypothetical teaching case — Question

Which diagnosis becomes especially important because of his age?

Teaching answer: Primary testicular lymphoma must be considered; Germ-cell tumors remain an important differential.

Slide 4 · Primary testicular lymphoma: The definition

A hematolymphoid malignancy presenting in the testis as the primary disease site.

The designation “primary” requires clinical staging and exclusion of dominant systemic lymphoma.

Histology establishes the lymphoma subtype; Location alone does not.

Slide 5 · An uncommon testicular malignancy

2%–5%

Of testicular neoplasms in the Robbins account

Despite its rarity overall, testicular lymphoma is a major diagnosis in older patients.

This estimate pertains to primary testicular lymphomas, not all lymphomas with testicular involvement.

Slide 6 · Age changes the leading differential

Most younger adult masses

Men older than 60 years

Germ-cell tumors dominate overall.

Seminoma and nonseminomatous GCTs are major categories.

Lymphoma becomes the most common testicular neoplasm in this age group.

A “classic GCT” presumption may be misleading.

Slide 7 · The main neoplastic lineages

Tumor family

Typical identity

Key diagnostic question

Germ-cell tumors

Seminoma and nonseminomatous GCTs

Germ-cell differentiation?

Sex cord–stromal tumors

Leydig and Sertoli lineages

Stromal / sex-cord differentiation?

Lymphomas

Mature B-cell or rarer other lineage

Hematolymphoid phenotype?

Slide 8 · Primary versus secondary testicular involvement

Primary testicular lymphoma

Secondary testicular lymphoma

Testis is the presenting dominant disease site.

Extragonadal disease may still be discovered on staging.

A pre-existing or predominant systemic lymphoma involves the testis.

The distinction requires chronology and distribution.

Slide 9 · Why “primary” cannot be assigned by microscopy alone

The same DLBCL morphology can occur in both primary and secondary testicular disease.

The clinical history and disease distribution define the primary site.

Diagnostic reporting should describe the observed histologic type without inferring unsupported chronology.

Slide 10 · The testis is an immune-privileged site

The testicular microenvironment restricts immune exposure to developing germ cells.

The blood–testis barrier is created largely by junctions between Sertoli cells.

Immune privilege modifies local immunity; It does not mean absolute immune isolation.

Slide 11 · Blood–testis barrier: Anatomic principle

Original conceptual schematic — not a histological specimen

Seminiferous tubule (conceptual cross-section)

Sertoli cells

Adluminal region

Basal region

Tight junctions between adjacent Sertoli cells

The barrier divides basal and adluminal environments.

Slide 12 · Immune privilege and lymphoma biology

Restricted immune surveillance

Selective survival pressures

Clonal immune-evasion traits

Conceptual sequence: Mechanisms vary by tumor; Not every case carries the same alterations.

Slide 13 · Anatomical immune barriers: The clinical connection

The testis and CNS occupy specialized immune environments.

Testicular DLBCL shares biological features with primary CNS / vitreoretinal large B-cell lymphomas.

These relationships help explain their distinctive relapse patterns, but do not establish a single metastatic route.

Slide 14 · WHO-HAEM5: Immune-privileged-site large B-cell lymphomas

Primary large B-cell lymphomas of immune-privileged sites form a shared classification group.

The WHO-HAEM5 group covers primary CNS, vitreoretinal, and testicular large B-cell lymphomas in immunocompetent hosts.

This grouping does not reclassify every testicular lymphoma as a large B-cell lymphoma.

Slide 15 · Three lymphoma types named by Robbins

Relative order in text

Histologic type

Major defining axis

Most common

Diffuse large B-cell lymphoma

Aggressive mature B-cell lymphoma

Next

Burkitt lymphoma

MYC-driven mature B-cell lymphoma

Next

EBV-positive extranodal NK/T-cell lymphoma

EBV-associated NK/T-cell lineage

Slide 16 · DLBCL is the principal testicular lymphoma subtype

Diffuse large B-cell lymphoma (DLBCL) is the diagnostic anchor.

DLBCL consists of sheets of transformed large B cells.

Primary testicular DLBCL commonly shows an activated B-cell / non-germinal-center phenotype.

Slide 17 · Do not equate subtype and site

DLBCL

Testicular DLBCL

Defined by large neoplastic B cells and diffuse growth.

Can arise at many nodal and extranodal sites.

DLBCL in a specific immune-privileged organ.

Distinct clinical behavior and recurrent molecular patterns.

Slide 18 · Burkitt lymphoma: An important alternative

Mature B-cell neoplasm with very high proliferative activity.

Characterized by rearrangement of MYC with immunoglobulin loci.

Typically shows a monomorphic intermediate-sized cytology and a prominent “starry-sky” pattern.

Testicular involvement is less frequent than DLBCL.

Slide 19 · EBV-positive extranodal NK/T-cell lymphoma

Listed among less frequent testicular lymphoma types.

It belongs to a different lineage from B-cell DLBCL and Burkitt lymphoma.

EBV demonstration and lineage-directed immunophenotyping become important in suspected cases.

Do not label a CD20-positive large B-cell tumor as NK/T lymphoma.

Slide 20 · Typical presentation: Testicular enlargement

A progressively enlarging, often painless testicular mass is a central presentation.

Clinically, the mass may resemble a germ-cell tumor or inflammatory enlargement.

Age and an infiltrative disease pattern should change the differential.

Slide 21 · Laterality is diagnostically useful

Testicular lymphoma may involve both testes.

That bilaterality is more frequent than in typical germ-cell tumors.

Contralateral involvement may be synchronous or appear later as relapse.

A clinically normal opposite testis does not eliminate future relapse risk.

Slide 22 · Spermatic-cord involvement

Frequent extension to the spermatic cord.

Pathologic assessment should document involvement when present.

Extension is a distribution finding, not an independent proof of lymphoma subtype.

Slide 23 · Potential sites of involvement and recurrence

Testis

Contralateral testis

Central nervous system

Other systemic sites

Boxes represent documented disease sites; Arrows denote clinical evaluation, not a proven obligatory sequence.

Slide 24 · The CNS is a critical relapse compartment

A high propensity for CNS involvement distinguishes testicular lymphoma.

CNS involvement as a frequent site of recurrence.

CNS risk informs staging, prevention strategies, and surveillance discussions.

Slide 25 · Relapse is not restricted to the first months

Testicular DLBCL may recur at extranodal sites after systemic therapy.

The contralateral testis and CNS merit specific attention.

Late relapse has been reported; A single fixed follow-up interval cannot summarize all risk.

Slide 26 · Testicular lymphoma versus germ-cell tumor

Germ-cell tumor pattern

Lymphoma pattern

Dominant testicular neoplasm group overall.

Serum AFP/hCG may aid GCT classification and management.

Especially important after age 60.

Bilateral and spermatic-cord involvement are characteristic clues.

Slide 27 · Solid testicular mass: Avoid casual sampling

Radical orchiectomy as the standard management of a suspected solid testicular neoplasm.

Transscrotal biopsy can cause tumor spillage in the germ-cell-tumor pathway.

An individualized tissue-acquisition strategy should be determined by the treating team when lymphoma is suspected.

Slide 28 · Clinical entry to a tissue diagnosis

Solid testicular lesion

Clinical assessment + imaging

Appropriate surgical tissue

Histology + IHC

A simplified educational pathway; Not a substitute for urologic/hematologic protocols.

Slide 29 · Macroscopic examination: Map the disease

A testicular specimen should be assessed for the mass and its extent.

Describe distribution in parenchyma, relation to the capsule and rete region, and spermatic-cord involvement.

Gross appearance alone is insufficient to subtype a lymphoma.

Slide 30 · Histologic pattern: Lymphoma within testicular tissue

Original schematic — not a clinical histology image

Neoplastic lymphoid cells

Residual / compressed tubular profiles

Slide 31 · DLBCL: Recognize the diffuse infiltrate

An involved tissue may be effaced by a diffuse infiltrate of large lymphoid cells.

Neoplastic nuclei may show open chromatin and prominent nucleoli.

Cell size, heterogeneity, apoptosis, and mitotic activity should all be assessed.

Slide 32 · Normal tubules versus lymphomatous infiltration

Expected architecture

Infiltrated testis

Seminiferous tubules separated by interstitium.

Tubular profiles are recognizable at low power.

Neoplastic lymphoid infiltrate expands the interstitium.

Tubules may become separated, compressed, or destroyed.

Slide 33 · Large B-cell cytology: What to describe

Cell size relative to adjacent small lymphocytes.

Nuclear shape and chromatin texture; Nucleolar prominence.

Degree of cytologic variation and mitotic activity.

Necrosis and residual testicular structures, if present.

Slide 34 · Atypical lymphoid infiltrate: First decisions

Determine whether the infiltrate is neoplastic or reactive.

Assess whether tumor cells show large B-cell, smaller monomorphic, or other morphology.

Use an immunophenotypic panel to confirm lineage rather than relying on nuclear size alone.

Slide 35 · A lineage-first immunohistochemistry strategy

Atypical cells

Hematolymphoid lineage?

B-cell versus other lineage

Subtype-defining studies

Conceptual strategy. Test selection depends on morphology and clinical context.

Slide 36 · Core immunophenotypic landmarks

Marker / method

Interpretive role

Limitation

CD20, PAX5, CD79a

Support B-cell differentiation

Expression must be interpreted in the tumor cells

CD10, BCL6, MUM1/IRF4

Characterize B-cell phenotype

No single marker proves testicular origin

Ki-67

Estimate proliferative fraction

High labeling is not a standalone diagnosis

EBER in situ hybridization

Detect EBV within cells

EBV status alone does not determine lineage

Slide 37 · Confirm B-cell lineage first

The immunophenotype establishes identity before detailed molecular classification.

Testicular DLBCL generally expresses mature B-cell antigens such as CD20 and PAX5.

A broad panel is safer than interpreting a single strongly positive stain.

Slide 38 · CD10, BCL6, and MUM1: Interpret together

These markers are used in immunohistochemical cell-of-origin algorithms.

Primary testicular DLBCL is commonly non-GCB / activated B-cell–like.

Protein-expression algorithms are surrogates, not identical to gene-expression profiling.

Variable staining does not by itself negate a testicular DLBCL diagnosis.

Slide 39 · Phenotype is not synonymous with genotype

IHC cell-of-origin surrogate

Molecular classification

CD10 / BCL6 / MUM1 may be used in a practical algorithm.

Results depend on assay and interpretive rules.

Recurrent mutation patterns inform tumor biology.

Genetic classes are not reducible to one IHC stain.

Slide 40 · Proliferation and Ki-67: Use with care

A high Ki-67 index is consistent with aggressive lymphoma.

Burkitt lymphoma commonly has a very high proliferation fraction.

Ki-67 alone cannot distinguish Burkitt lymphoma from other high-grade B-cell neoplasms.

Quantitative percentages should reflect an actual measured specimen, not a textbook stereotype.

Slide 41 · Recurrent MYD88 and CD79B alterations

Testicular large B-cell lymphomas frequently show B-cell signaling pathway alterations.

MYD88 and CD79B are recurrently altered in immune-privileged-site large B-cell lymphomas.

They support a shared biological profile; Neither alteration is mandatory in every case.

Slide 42 · A simplified B-cell survival pathway

B-cell receptor signaling (CD79B)

MYD88-associated innate signaling

NF-κB activation

Growth / survival advantage

Schematic integration of recurrent biology, not an assay-based diagnosis.

Slide 43 · Immune escape is part of the biological picture

Genetic changes affecting antigen presentation and immune recognition occur in this lymphoma group.

Alterations involving the PD-L1 / PD-L2 axis have been described.

These are biological findings; They do not automatically establish responsiveness to a checkpoint inhibitor.

Slide 44 · Diagnostic versus prognostic versus predictive

Diagnostic / characterizing evidence

Outcome / therapeutic implications

Morphology plus B-cell markers establishes a mature B-cell lymphoma.

Genetic findings may refine biological classification.

Clinical stage and CNS risk affect management.

A therapeutic prediction requires validated evidence for that treatment context.

Slide 45 · Burkitt: Why MYC matters

Burkitt lymphoma is driven by MYC rearrangement, commonly with IGH or an immunoglobulin light-chain locus.

MYC stimulates metabolic and transcriptional programs needed for rapid growth.

It is important to distinguish this entity from DLBCL with high MYC expression or rearrangement.

Slide 46 · Burkitt morphology: “starry sky”

A uniform field of rapidly proliferating tumor cells is punctuated by pale macrophages.

Numerous apoptotic bodies are phagocytosed by benign tingible-body macrophages.

The pattern is suggestive but not pathognomonic for Burkitt lymphoma.

Slide 47 · Burkitt immunophenotype and genetics

Dimension

Typical finding

Diagnostic interpretation

Lineage

Mature B-cell markers, CD20

B-cell origin

Germinal-center program

CD10 and BCL6

Supports GC phenotype

Apoptosis / growth

Often BCL2-negative, very high proliferation

Biologically coherent, not unique

Defining genetics

MYC rearrangement

Needs context; Avoid MYC-only classification

Slide 48 · When the tumor is not B-cell DLBCL

Rarer lineages require a fresh diagnostic approach.

An EBV-positive extranodal NK/T-cell process is explicitly included in the Robbins testicular lymphoma spectrum.

EBER in situ hybridization and appropriate T/NK-associated markers are useful in lineage workup.

The exact panel follows morphology and local hematopathology practice.

Slide 49 · Subtype comparison: High-yield distinctions

Type

Morphologic tendency

Strongest contextual clues

DLBCL

Pleomorphic large lymphoid cells

Mature B-cell phenotype; Commonest type

Burkitt

Monomorphic, intermediate-sized cells; Starry sky

MYC-driven biology, GC B-cell phenotype

Extranodal NK/T

Not a mature B-cell tumor

EBV association and NK/T lineage studies

Slide 50 · Seminoma versus lymphoma

Feature

Seminoma

Testicular DLBCL

Usual clinical context

Younger adult testicular tumor

Particularly important in older men

Tumor lineage

Germ-cell differentiation

Mature lymphoid B-cell differentiation

Architecture

Germ-cell tumor pattern

Diffuse lymphoid infiltration

Useful phenotype

Germ-cell marker panel

CD20 / PAX5 and lymphoma panel

Slide 51 · Other germ-cell and non-GCT differentials

Embryonal carcinoma and mixed germ-cell tumors require germ-cell lineage assessment.

Leydig and Sertoli cell neoplasms can mimic a solid testicular malignancy grossly.

Immunophenotype and architecture are more reliable than gross appearance alone.

AFP and hCG belong to the germ-cell tumor workup; They do not establish lymphoma subtype.

Slide 52 · Inflammation versus neoplastic infiltration

Inflammatory orchitis

Lymphoma

Mixed inflammatory cells and accompanying tissue response may occur.

Clinical infection context can support a reactive process.

A destructive or monomorphic atypical lymphoid infiltrate increases concern.

Clonality and immunophenotype may be needed in difficult cases.

Slide 53 · A diagnostic pitfall: Reactive background cells

Large neoplastic B cells may be intermixed with reactive T lymphocytes and histiocytes.

Identify which cells carry the lineage-marker signal.

A sparse tumor population can be missed if the entire infiltrate is interpreted as benign.

Slide 54 · A diagnostic pitfall: “CD20-positive” is not enough

B-cell lineage does not distinguish DLBCL from all other mature B-cell lymphomas.

Morphology, proliferation, other immunostains, and molecular findings may be needed.

Clinical disease distribution distinguishes primary from secondary testicular involvement.

Slide 55 · The useful pathology report

Element

What to communicate

Histologic diagnosis

Lymphoma lineage and most defensible subtype

Immunophenotype

Relevant positives, negatives, and interpretive limitations

Tumor distribution

Parenchyma, tunica / adjacent tissue, spermatic cord if sampled

Uncertainty

Pending studies and limitations of tissue sampling

Slide 56 · Staging question: Testicular-only or disseminated?

Tissue confirms lymphoma

History + imaging + labs

Assess extracompartmental sites

Assign extent / plan care

Primary versus secondary designation and treatment require clinical staging; Specifics follow the treating team.

Slide 57 · CNS assessment: Why it enters the initial workup

Testicular lymphoma carries a distinct propensity for CNS relapse.

Symptoms and baseline risk guide the neurological assessment and staging discussion.

Decisions about CSF testing or neuroimaging depend on current clinical guidance and the individual patient.

Slide 58 · Pathology initiates a multidisciplinary pathway

A tissue diagnosis is the beginning of integrated disease management.

Urology, hematopathology, hematology/oncology, radiation oncology, and neurology/neuro-oncology may contribute.

High CNS and contralateral testis risks require explicit care planning.

Slide 59 · Orchiectomy: Diagnostic and local-control roles

Radical inguinal orchiectomy commonly provides definitive tissue diagnosis and local control.

Systemic lymphoma treatment is generally required beyond surgery alone.

Gross and histologic assessment should identify disease extent in the resected specimen.

Slide 60 · Integrated treatment framework

Orchiectomy / tissue diagnosis

Systemic immunochemotherapy

CNS-directed prevention plan

Contralateral testis protection

Treatment is individualized; This is a conceptual overview, not a prescription.

Slide 61 · Why systemic treatment is necessary

Localized surgery cannot address occult lymphoma cells outside the testis.

Rituximab-containing chemotherapy is generally used for CD20-positive testicular DLBCL.

Exact regimen, intensity, and supportive care reflect stage, fitness, and current protocols.

Slide 62 · CNS-directed prophylaxis: Rationale and limits

Historical and contemporary regimens often incorporate CNS prophylaxis for testicular DLBCL.

Intrathecal and/or systemic methotrexate-based approaches require specialist selection.

The optimal prevention strategy remains an area of debate; Avoid presenting one pathway as universally proven.

Slide 63 · Protecting the contralateral testis

Contralateral testicular relapse is a distinctive concern.

Prophylactic radiation to the uninvolved contralateral testis is included in many multimodality treatment protocols.

The risk–benefit discussion includes age, hormonal function, fertility, and individual treatment context.

Slide 64 · Longitudinal clinical surveillance

Disease control must be evaluated systemically and at extranodal risk sites.

New neurological symptoms warrant attention because CNS relapse is clinically consequential.

New contralateral testicular findings require prompt assessment.

Follow-up schedules should be derived from current clinical protocols rather than invented here.

Slide 65 · What pathology can and cannot predict alone

Pathology can establish

Requires clinical integration

Lymphoma type and immunophenotype.

Molecular features when tested.

Anatomic spread within the resection specimen.

Full disease stage.

Individual CNS relapse risk.

Best treatment plan and outcome probability.

Slide 66 · Case exercise: Older patient

A man in his seventh decade has a firm testicular mass. The tissue shows diffuse sheets of large CD20-positive lymphoid cells.

Hypothetical teaching case — Question

Which diagnosis is the leading histologic consideration?

Teaching answer: DLBCL involving the testis. Staging is necessary before assigning “primary testicular” disease.

Slide 67 · Case exercise: Bilateral disease

An older man with testicular DLBCL is subsequently found to have a lesion in the opposite testis.

Hypothetical teaching case — Question

Which clinical feature of testicular lymphoma does this illustrate?

Teaching answer: The propensity for bilateral / contralateral testicular involvement. Reassessment for systemic and CNS disease is essential.

Slide 68 · Case exercise: High proliferation

A testicular lymphoma shows monomorphic intermediate-sized cells, abundant apoptotic debris, and very high proliferative activity.

Hypothetical teaching case — Question

Which additional lymphoma subtype should be actively excluded?

Teaching answer: Burkitt lymphoma; Evaluate its mature B-cell phenotype and MYC-driven genetic context.

Slide 69 · Common errors to avoid

Calling every solid testicular mass a germ-cell tumor.

Calling a lymphoma primary based on pathology alone.

Using a single marker to determine hematolymphoid subtype.

Ignoring contralateral testicular and CNS relapse patterns.

Slide 70 · Diagnostic synthesis: The clinical-pathology loop

Older patient with solid testicular mass

Clinical and imaging assessment

Histology shows atypical lymphoid cells

Confirm B-cell vs other lineage

Subtype and characterize

DLBCL; Exclude Burkitt and rarer variants

Integrate staging

Primary vs secondary; CNS and contralateral risks

Slide 71 · Final synthesis

Rare overall, but the leading testicular neoplasm in men older than 60 years.

DLBCL predominates; Burkitt and EBV-positive extranodal NK/T-cell lymphoma are rarer.

Diffuse lymphoid infiltration plus an appropriate immunophenotype establish tissue identity.

CNS and contralateral testicular involvement make this an organ-specific lymphoma problem.

Slide 72 · Selected references and source boundaries

Primary textbook: Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. (2026). Chapter 21, p. 886; germ-cell tumor context pp. 881–886.

Textbook background: Robbins, Cotran & Kumar. Chapter 13, pp. 546–548: DLBCL and Burkitt lymphoma.

2021 review: Testicular Diffuse Large B-Cell Lymphoma—Clinical, Molecular, and Immunological Features. Cancers. PMCID: PMC8392512.

2024 review: Primary large B-cell lymphomas of immune-privileged sites. Blood. PMID: 38635786.

2025 review: Primary testicular lymphoma. Cancer Treatment Reviews. 136:102927. DOI: 10.1016/j.ctrv.2025.102927.