HAEM5:Splenic diffuse red pulp small B-cell lymphoma

Haematolymphoid Tumours (WHO Classification, 5th ed.)

editContent Update To WHO 5th Edition Classification Is In Process; Content Below is Based on WHO 4th Edition Classification

This page was converted to the new template on 2023-12-07. The original page can be found at HAEM4:Splenic Diffuse Red Pulp Small B-cell Lymphoma.

(General Instructions – The focus of these pages is the clinically significant genetic alterations in each disease type. This is based on up-to-date knowledge from multiple resources such as PubMed and the WHO classification books. The CCGA is meant to be a supplemental resource to the WHO classification books; the CCGA captures in a continually updated wiki-stye manner the current genetics/genomics knowledge of each disease, which evolves more rapidly than books can be revised and published. If the same disease is described in multiple WHO classification books, the genetics-related information for that disease will be consolidated into a single main page that has this template (other pages would only contain a link to this main page). Use HUGO-approved gene names and symbols (italicized when appropriate), HGVS-based nomenclature for variants, as well as generic names of drugs and testing platforms or assays if applicable. Please complete tables whenever possible and do not delete them (add N/A if not applicable in the table and delete the examples); to add (or move) a row or column in a table, click nearby within the table and select the > symbol that appears. Please do not delete or alter the section headings. The use of bullet points alongside short blocks of text rather than only large paragraphs is encouraged. Additional instructions below in italicized blue text should not be included in the final page content. Please also see Author_Instructions and FAQs as well as contact your Associate Editor or Technical Support.)

Primary Author(s)*

• Snehal Patel, MD, PhD

WHO Classification of Disease

Structure	Disease
Book	Haematolymphoid Tumours (5th ed.)
Category	B-cell lymphoid proliferations and lymphomas
Family	Mature B-cell neoplasms
Type	Splenic B-cell lymphomas and leukaemias
Subtype(s)	Splenic diffuse red pulp small B-cell lymphoma

Definition / Description of Disease

• Splenic diffuse red pulp small B-cell lymphoma (SDRPL) is an extremely rare indolent B-cell neoplasm of adults (provisional WHO entity)
• Name derives from diffuse involvement of the splenic red pulp by small mature-appearing B-cells
• Marked splenomegaly and marrow infiltration result in left flank discomfort, fatigue, and susceptibility to infections

Synonyms / Terminology

• Splenic marginal zone lymphoma, diffuse variant
• Splenic red pulp lymphoma with numerous basophilic villous lymphocytes
• Splenic lymphoma with villous lymphocytes

Epidemiology / Prevalence

• <1% of all non-Hodgkin lymphomas
• Median age ~ 66 to 80 years
• M:F 1.8:1 to 2.4:1

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Clinical Features

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Signs and Symptoms	EXAMPLE: Asymptomatic (incidental finding on complete blood counts) EXAMPLE: B-symptoms (weight loss, fever, night sweats) EXAMPLE: Fatigue EXAMPLE: Lymphadenopathy (uncommon)
Laboratory Findings	EXAMPLE: Cytopenias EXAMPLE: Lymphocytosis (low level)

editv4:Clinical Features

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Signs & Symptoms

• Splenic enlargement and/or discomfort
• Fatigue
• B-symptoms - weight loss, fever, night sweats (variable)
• Lymphadenopathy (uncommon)

Laboratory findings

• Cytopenias (uncommon)
• Lymphocytosis (moderate)
• No monocytopenia

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Sites of Involvement

• Spleen (red pulp)
• Bone marrow (sinusoidal > interstitial)
• Blood
• Liver
• Lymph node (uncommon)

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Morphologic Features

• Monomorphic small lymphocytes
• Villous projections
• Scant cytoplasm
• Condensed chromatin
• Smooth nuclear contours
• Inconspicuous nucleoli
• Involvement of red pulp (cords & sinusoids)
• Residual white pulp
• No/minimal reticulin fibrosis

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Immunophenotype

Finding	Marker
Positive (B-cell lineage markers)	CD19, CD20 (bright), CD22, CD79a, CD79b, PAX5, FMC7, sIg (monotypic), IgG
Positive	DBA-44, BCL2 (weak), CD11c*
Negative	CD5, CD10, CD23, BCL1, BCL6
Negative (HCL markers)	CD25, CD43, CD103 (variable), CD123, CD138, CD200, annexin A1, TRAP
MIB-1 proliferative index	2-4%

*Reports of CD11c expression are conflicting in the literature.

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WHO Essential and Desirable Genetic Diagnostic Criteria

(Instructions: The table will have the diagnostic criteria from the WHO book autocompleted; remove any non-genetics related criteria. If applicable, add text about other classification systems that define this entity and specify how the genetics-related criteria differ.)

WHO Essential Criteria (Genetics)*
WHO Desirable Criteria (Genetics)*
Other Classification

*Note: These are only the genetic/genomic criteria. Additional diagnostic criteria can be found in the WHO Classification of Tumours.

Related Terminology

(Instructions: The table will have the related terminology from the WHO autocompleted.)

Acceptable
Not Recommended

Gene Rearrangements

Put your text here and fill in the table (Instructions: Details on clinical significance such as prognosis and other important information can be provided in the notes section. Please include references throughout the table. Do not delete the table.)

Driver Gene	Fusion(s) and Common Partner Genes	Molecular Pathogenesis	Typical Chromosomal Alteration(s)	Prevalence -Common >20%, Recurrent 5-20% or Rare <5% (Disease)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE: ABL1	EXAMPLE: BCR::ABL1	EXAMPLE: The pathogenic derivative is the der(22) resulting in fusion of 5’ BCR and 3’ABL1.	EXAMPLE: t(9;22)(q34;q11.2)	EXAMPLE: Common (CML)	EXAMPLE: D, P, T	EXAMPLE: Yes (WHO, NCCN)	EXAMPLE: The t(9;22) is diagnostic of CML in the appropriate morphology and clinical context (add reference). This fusion is responsive to targeted therapy such as Imatinib (Gleevec) (add reference). BCR::ABL1 is generally favorable in CML (add reference).
EXAMPLE: CIC	EXAMPLE: CIC::DUX4	EXAMPLE: Typically, the last exon of CIC is fused to DUX4. The fusion breakpoint in CIC is usually intra-exonic and removes an inhibitory sequence, upregulating PEA3 genes downstream of CIC including ETV1, ETV4, and ETV5.	EXAMPLE: t(4;19)(q25;q13)	EXAMPLE: Common (CIC-rearranged sarcoma)	EXAMPLE: D		EXAMPLE: DUX4 has many homologous genes; an alternate translocation in a minority of cases is t(10;19), but this is usually indistinguishable from t(4;19) by short-read sequencing (add references).
EXAMPLE: ALK	EXAMPLE: ELM4::ALK Other fusion partners include KIF5B, NPM1, STRN, TFG, TPM3, CLTC, KLC1	EXAMPLE: Fusions result in constitutive activation of the ALK tyrosine kinase. The most common ALK fusion is EML4::ALK, with breakpoints in intron 19 of ALK. At the transcript level, a variable (5’) partner gene is fused to 3’ ALK at exon 20. Rarely, ALK fusions contain exon 19 due to breakpoints in intron 18.	EXAMPLE: N/A	EXAMPLE: Rare (Lung adenocarcinoma)	EXAMPLE: T		EXAMPLE: Both balanced and unbalanced forms are observed by FISH (add references).
EXAMPLE: ABL1	EXAMPLE: N/A	EXAMPLE: Intragenic deletion of exons 2–7 in EGFR removes the ligand-binding domain, resulting in a constitutively active tyrosine kinase with downstream activation of multiple oncogenic pathways.	EXAMPLE: N/A	EXAMPLE: Recurrent (IDH-wildtype Glioblastoma)	EXAMPLE: D, P, T

editv4:Chromosomal Rearrangements (Gene Fusions)

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• No consistent gene fusion

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editv4:Clinical Significance (Diagnosis, Prognosis and Therapeutic Implications).

Please incorporate this section into the relevant tables found in:

• Chromosomal Rearrangements (Gene Fusions)
• Individual Region Genomic Gain/Loss/LOH
• Characteristic Chromosomal Patterns
• Gene Mutations (SNV/INDEL)

Alteration	Significance	Note
BRAF p.Val600Glu	Possible role in diagnosis (exclusion)	Prevalent in HCL but rare/absent in SDRPL
MAP2K1	Possible role in diagnosis (exclusion)	Prevalent in HCL-v and a subset of cases classified as HCL but uncommon in SDRPL
KLF2 and TNFAIP3	Possible role in diagnosis (exclusion)	Prevalent in SMZL but rare/absent in SDRPL
MYD88	Possible role in diagnosis (exclusion)	Prevalent in LPL and SMZL but rare/absent in SDRPL
BCOR	Possible role in diagnosis (inclusion)	Prevalent in SDRPL but rare/absent in HCL, HCL-v, and SMZL

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Individual Region Genomic Gain/Loss/LOH

Put your text here and fill in the table (Instructions: Includes aberrations not involving gene rearrangements. Details on clinical significance such as prognosis and other important information can be provided in the notes section. Can refer to CGC workgroup tables as linked on the homepage if applicable. Please include references throughout the table. Do not delete the table.)

Chr #	Gain, Loss, Amp, LOH	Minimal Region Cytoband and/or Genomic Coordinates [Genome Build; Size]	Relevant Gene(s)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE: 7	EXAMPLE: Loss	EXAMPLE: chr7	EXAMPLE: Unknown	EXAMPLE: D, P	EXAMPLE: No	EXAMPLE: Presence of monosomy 7 (or 7q deletion) is sufficient for a diagnosis of AML with MDS-related changes when there is ≥20% blasts and no prior therapy (add reference).  Monosomy 7/7q deletion is associated with a poor prognosis in AML (add references).
EXAMPLE: 8	EXAMPLE: Gain	EXAMPLE: chr8	EXAMPLE: Unknown	EXAMPLE: D, P		EXAMPLE: Common recurrent secondary finding for t(8;21) (add references).
EXAMPLE: 17	EXAMPLE: Amp	EXAMPLE: 17q12; chr17:39,700,064-39,728,658 [hg38; 28.6 kb]	EXAMPLE: ERBB2	EXAMPLE: D, P, T		EXAMPLE: Amplification of ERBB2 is associated with HER2 overexpression in HER2 positive breast cancer (add references). Add criteria for how amplification is defined.

editv4:Genomic Gain/Loss/LOH

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• In a study of 13 cases, 10q23, 14q31-q32, and 17p13 deletions in 3 cases; 9p21 deletions in 2 cases; 7q31.3-q32.3 deletion in 1 case; no trisomies 3 or 18
• In a study of 24 cases, 7q deletion in 6 cases; trisomy 3 and 18 in 1 case; trisomy 12 in 3 case

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Characteristic Chromosomal or Other Global Mutational Patterns

Put your text here and fill in the table (Instructions: Included in this category are alterations such as hyperdiploid; gain of odd number chromosomes including typically chromosome 1, 3, 5, 7, 11, and 17; co-deletion of 1p and 19q; complex karyotypes without characteristic genetic findings; chromothripsis; microsatellite instability; homologous recombination deficiency; mutational signature pattern; etc. Details on clinical significance such as prognosis and other important information can be provided in the notes section. Please include references throughout the table. Do not delete the table.)

Chromosomal Pattern	Molecular Pathogenesis	Prevalence - Common >20%, Recurrent 5-20% or Rare <5% (Disease)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE: Co-deletion of 1p and 18q	EXAMPLE: See chromosomal rearrangements table as this pattern is due to an unbalanced derivative translocation associated with oligodendroglioma (add reference).	EXAMPLE: Common (Oligodendroglioma)	EXAMPLE: D, P
EXAMPLE: Microsatellite instability - hypermutated		EXAMPLE: Common (Endometrial carcinoma)	EXAMPLE: P, T

editv4:Characteristic Chromosomal Aberrations / Patterns

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• BCOR copy number loss in 10% and often with BCOR point mutations
• Copy number alterations in 69%
• Complex karyotypes in 13%

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Gene Mutations (SNV/INDEL)

Put your text here and fill in the table (Instructions: This table is not meant to be an exhaustive list; please include only genes/alterations that are recurrent or common as well either disease defining and/or clinically significant. If a gene has multiple mechanisms depending on the type or site of the alteration, add multiple entries in the table. For clinical significance, denote associations with FDA-approved therapy (not an extensive list of applicable drugs) and NCCN or other national guidelines if applicable; Can also refer to CGC workgroup tables as linked on the homepage if applicable as well as any high impact papers or reviews of gene mutations in this entity. Details on clinical significance such as prognosis and other important information such as concomitant and mutually exclusive mutations can be provided in the notes section. Please include references throughout the table. Do not delete the table.)

Gene	Genetic Alteration	Tumor Suppressor Gene, Oncogene, Other	Prevalence - Common >20%, Recurrent 5-20% or Rare <5% (Disease)	Diagnostic, Prognostic, and Therapeutic Significance - D, P, T	Established Clinical Significance Per Guidelines - Yes or No (Source)	Clinical Relevance Details/Other Notes
EXAMPLE:EGFR	EXAMPLE: Exon 18-21 activating mutations	EXAMPLE: Oncogene	EXAMPLE: Common (lung cancer)	EXAMPLE: T	EXAMPLE: Yes (NCCN)	EXAMPLE: Exons 18, 19, and 21 mutations are targetable for therapy. Exon 20 T790M variants cause resistance to first generation TKI therapy and are targetable by second and third generation TKIs (add references).
EXAMPLE: TP53; Variable LOF mutations	EXAMPLE: Variable LOF mutations	EXAMPLE: Tumor Supressor Gene	EXAMPLE: Common (breast cancer)	EXAMPLE: P		EXAMPLE: >90% are somatic; rare germline alterations associated with Li-Fraumeni syndrome (add reference). Denotes a poor prognosis in breast cancer.
EXAMPLE: BRAF; Activating mutations	EXAMPLE: Activating mutations	EXAMPLE: Oncogene	EXAMPLE: Common (melanoma)	EXAMPLE: T

Note: A more extensive list of mutations can be found in cBioportal, COSMIC, and/or other databases. When applicable, gene-specific pages within the CCGA site directly link to pertinent external content.

editv4:Gene Mutations (SNV/INDEL)

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Gene*	Oncogene/Tumor Suppressor/Other	Presumed Mechanism (LOF/GOF/Other; Driver/Passenger)	Prevalence
CCND3	Oncogene	GOF	21%
BCOR	Tumor Suppressor	LOF	14%

^‡Specific mutations in these genes can be found in cBioPortal, COSMIC, and elsewhere

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Epigenomic Alterations

• Not studied

Genes and Main Pathways Involved

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Gene; Genetic Alteration	Pathway	Pathophysiologic Outcome
EXAMPLE: BRAF and MAP2K1; Activating mutations	EXAMPLE: MAPK signaling	EXAMPLE: Increased cell growth and proliferation
EXAMPLE: CDKN2A; Inactivating mutations	EXAMPLE: Cell cycle regulation	EXAMPLE: Unregulated cell division
EXAMPLE: KMT2C and ARID1A; Inactivating mutations	EXAMPLE: Histone modification, chromatin remodeling	EXAMPLE: Abnormal gene expression program

editv4:Genes and Main Pathways Involved

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Molecular feature	Pathway
BCOR LoF alterations (point mutations & copy number loss; 24% of SDRPL)	germinal center formation & apoptosis
CCND3 GoF alterations (point mutations; 21% of SDRPL)	cell cycle regulation

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Genetic Diagnostic Testing Methods

• SDRPL is a provisional WHO entity and definitive diagnostic criteria have not been determined
  • Diagnosis of exclusion
    • Differential of splenic lymphomas with cytoplasmic projections: HCL, HCL-v, SMZL
  • Distinction is by clinical history, morphology, and immunohistochemistry
    • No pathognomonic diagnostic markers (molecular or otherwise)
    • Mutations seen in other entities in DDx are absent/rare in SDRPL and vice versa and may be diagnostically useful (see Clinical Significance below)
      • Next-generation sequencing with targeted lymphoid malignancy panels or exome sequencing may be considered in challenging cases

Familial Forms

• Not described

Additional Information

• None

Links

• HAEM5:Hairy cell leukaemia
• HAEM5:Hairy cell leukaemia Variant
• HAEM4:Splenic B-cell Lymphoma/Leukemia, Unclassifiable
• HAEM5:Splenic marginal zone lymphoma

References

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Notes

*Primary authors will typically be those that initially create and complete the content of a page.  If a subsequent user modifies the content and feels the effort put forth is of high enough significance to warrant listing in the authorship section, please contact the Associate Editor or other CCGA representative.  When pages have a major update, the new author will be acknowledged at the beginning of the page, and those who contributed previously will be acknowledged below as a prior author.

Prior Author(s):

*Citation of this Page: “Splenic diffuse red pulp small B-cell lymphoma”. Compendium of Cancer Genome Aberrations (CCGA), Cancer Genomics Consortium (CGC), updated 02/10/2025, https://ccga.io/index.php/HAEM5:Splenic_diffuse_red_pulp_small_B-cell_lymphoma.