Lymphoma & related disorders
Mature B cell neoplasms
Small B cell lymphomas with lymphoplasmacytic differentiation / marginal zone lymphomas
Splenic marginal zone


Topic Completed: 10 February 2020

Minor changes: 5 July 2020

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PubMed Search: Splenic marginal zone B cell lymphoma[TIAB]


Hatem Kaseb, M.D., Ph.D., M.P.H.
Stanley David Hudnall, M.D.
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Cite this page: Kaseb H, Hudnall S. Splenic marginal zone. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lymphomasplenicmzl.html. Accessed August 3rd, 2020.
Definition / general
  • Splenic marginal zone lymphoma (SMZL) is a low grade B cell neoplasm composed of small lymphocytes that originate from the splenic white pulp germinal centers
  • Marginal zone: light zone surrounding splenic follicles which contains post follicular memory B cells derived after stimulation of recirculating cells from T cell dependent antigen
Essential features
  • Splenic marginal zone lymphoma is a low grade B cell neoplasm composed of small lymphocytes that originate from the splenic white pulp germinal centers
    • The spleen and bone marrow are infiltrated by a micronodule that replaces the pre-existing lymphoid follicles and show marginal zone differentiation
  • Patients usually present with splenomegaly and no lymphadenopathy
  • The clinical, immunophenotypic, and genetic features of splenic marginal zone lymphoma are different from other marginal zone lymphomas, indicating that splenic marginal zone lymphoma is a distinct clinicopathologic entity, unrelated to mucosa associated lymphoid tissue or nodal marginal zone lymphomas (Jaffe: Hematopathology, 2nd Edition, 2017)
Terminology
  • Splenic B cell marginal zone lymphoma; splenic lymphoma with villous lymphocytes; splenic lymphoma with circulating villous lymphocytes
ICD coding
  • ICD-10: C83.07 - small cell B cell lymphoma, spleen
Epidemiology
Pathophysiology
  • Splenic marginal zone lymphoma pathogenesis involves antigen or superantigen stimulation and molecular deregulation of different genes (including NOTCH2 and KLF2) involved in normal lymphocyte differentiation (Blood 2016;127:2072)
  • Some splenic marginal zone lymphoma patients with hepatitis C seem to have better disease control with hepatitis C treatment, suggesting a possible role for hepatitis C in disease
Clinical features
Prognostic factors
Case reports
Treatment
  • Close observation (watch and wait) is advisable for asymptomatic patients (Blood 2016;127:2072)
  • Symptomatic
    • Rituximab:
      • Rituximab monotherapy is treatment of choice
      • Rituximab with or without splenectomy has been found to be an effective treatment modality (Blood 2018;132:666)
    • Resistant or relapsed patients
      • Chemotherapy: fludarabine or chlorambucil
    • Splenectomy
      • Indicated in patients refractory to immunochemotherapy
      • Is associated with a better disease outcome
    • HCV patients: appropriate viral eradication is associated with splenic marginal zone lymphoma remission
Gross description
  • Multiple small, grayish-white nodules due to marked expansion of the white pulp and infiltration of the red pulp
Gross images

Images hosted on other servers:

Markedly enlarged spleen with nodular cut surface

Microscopic (histologic) description
  • Spleen (Swerdlow: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th Edition, 2017)
    • Micronodular lymphoid infiltrate in which white pulp follicles
      • Infiltration by two cells types: small lymphocytes and marginal zone cells
        • The cells are often more admixed, leading to mixed mantle zone and marginal zone involvement pattern
      • Infiltration of small atypical lymphocytes in mantle zone and medium lymphocytes with pale cytoplasm and oval clear nucleus in marginal zone
    • The red pulp is usually infiltrated in both the cords and the sinuses; the pattern of infiltration is usually diffuse
    • Variable follicular colonization but definite increase in white pulp
    • Cells are centrocyte-like, monocytoid or lymphoplasmacytic
    • < 20% immunoblasts; involves red pulp also
  • Bone marrow (Jaffe: Hematopathology, 2nd Edition, 2016)
    • Combination of nodular, interstitial and intrasinusoidal is the most common pattern
    • Intrasinusoidal and interstitial infiltrate
      • Common in early stage
      • Intrasinusoidal infiltration of bone marrow is relatively specific finding
    • Nodular pattern is typical encountered with disease progression
    • In advanced disease, a combination of intrasinusoidal, interstitial and nodular infiltration is seen
  • Peripheral smear
    • Cells with scant cytoplasm and cleaved nucleus; confirm neoplastic with flow cytometry
Microscopic (histologic) images

Contributed by Hatem Kaseb, M.D., Ph.D., M.P.H.

Lymphoid aggregate

Peripheral smear images

Contributed by Hatem Kaseb, M.D., Ph.D., M.P.H.

Atypical lymphocytes

Molecular / cytogenetics description
Sample pathology report
  • Bone marrow, biopsy and aspirate:
    • Low grade non-Hodgkin B cell lymphoma, with features most suggestive of splenic marginal zone lymphoma (see comment)
    • Comment: Given the pattern of infiltration (nodular and intrasinusoidal) as well as cytomorphology of some lymphocytes with villous cytoplasmic projections and radiographic history of mild splenomegaly, features are most suggestive of a splenic marginal zone lymphoma. Correlation with clinical, cytogenetic and laboratory findings is recommended.
    • CBC (3/14/18) by report: HGB: 12.1 g/dL, MCV: 84.9 fL, WBC: 24.8 K/uL, PLT: 109 K/uL
  • Bone marrow biopsy:
    • Variably cellular overall normocellular marrow for age (30% cellular). Approximately 40% of the cellularity is comprised of large paratrabecular lymphoid aggregates and scattered interstitial lymphoid aggregates composed of small lymphocytes. Megakaryocytes are normal in number and morphology; the myeloid:erythroid (M:E) ratio is normal. Erythroid elements exhibit normal maturation; myeloid elements exhibit normal maturation. Granulomas are not seen; reticulin stain reveals that reticulin is mildly increased in association with the lymphoid aggregates. Trabecular bone is unremarkable.
  • Immunostains:
    • CD20 and CD19 highlight B cell comprising the majority of lymphocytes within the lymphoid aggregates with intrasinusoidal infiltration. Scattered CD3 positive T cells are present.
  • Bone marrow aspirate:
    • The marrow aspirate smears are spicular and paucicellular; scattered lymphocytes with occasional fine cytoplasmic projections present. Megakaryocytes are rare; the myeloid:erythroid (M:E) ratio is approximately 1:1; erythroid maturation is present.
    • Myeloid maturation is present. Prussian blue iron stain shows trace storage iron and no significant increase in ring sideroblasts.
    • Aspirate cell count: a 202 cell count reveals < 1% blasts, 6% promyelocytes / myelocytes, 32% maturing granulocyte forms, 16% erythroid forms, 38% lymphocytes, 3% plasma cells, 3% eosinophils and 2% monocytes.
Differential diagnosis
Board review style question #1

    What is the most common cytogenetic abnormality in splenic marginal zone lymphoma (SMZL)?

  1. Amp 22
  2. Del 7q
  3. Del 11q
  4. t (8;14)
Board review answer #1
B. Deletion 7q is identified in up to 40% of splenic marginal zone lymphoma patients.

Reference: Splenic marginal zone B cell lymphoma

Comment Here
Board review style question #2
    What is the immunophenotypic pattern of splenic marginal zone lymphoma (SMZL)?

  1. CD19+, CD20+, CD5-, CD23-
  2. CD19+, CD20+, CD5+, CD23+
  3. CD19+, CD20+, CD10+, BCL6+
  4. CD19+, CD20+, CD10+, BCL6+
Board review answer #2
A. CD19+, CD20+, CD5-, CD23- is consistent with splenic marginal zone lymphoma.

Reference: Splenic marginal zone B cell lymphoma

Comment Here
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