Spenic Marginal Zone Lymphoma (SMZL)

Splenic Marginal Zone Lymphoma (SMZL) is a B-cell lymphoma, which primarily affects the spleen and bone marrow.  The peripheral blood can also be involved by the so-called villous lymphocytes.  SMZL is rare (<2% of lymphomas) and has a non-distinct immunophenotype.


Diagnostic Features
  • Splenomegaly, often with involvement of hilar nodes and bone marrow
  • Nonspecific B-cell immunophenotype (negative for CD5, CD10, CD23, CD43, and annexin A1.
  • Histology shows a characteristic expanded rim around the white pulp area which has a paler appearance due to the relatively larger amount of cytoplasm within the neoplastic lymphocyte. This paler area is referred to as the marginal zone, and is the characteristic the gives this lymphoma its name . This architectural pattern is not seen outside the spleen.

Photomicrographs
Splenic Marginal Zone Lymphoma
Low power view demonstrating the prominent marginal zone and expanded white pulp area in a case of splenic marginal zone lymphoma.
Splenic Marginal Zone Lymphoma
High power view of the marginal zone of the spleen in a case of splenic marginal zone lymphoma.
Splenic Marginal Zone Lymphoma
Prominent marginal zones present in the spleen in a case of splenic marginal zone lymphoma.
Immunohistochemical Expression Pattern
Negative
Negative (rare + cases)
Negative
Positive
Negative
Negative
CD103
Flow Marker – Usually negative
Negative: + in Hairy Cell Leukemia
Negative
Targetoid pattern with increased positivity in the germinal centers and marginal zone areas.
Negative

References
Swerdlow SH, Campo E, Harris, NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):  WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017
 
Hematopathology. [edited by] Jaffe, ES. 1st. ed. Elsevier, Inc. © 2011. pp.184-187.
 
Parker, A., et. al.  “Best Practice in Lymphoma Diagnosis and Reporting.”  British Committee for Standards in Haematology, Royal College of Pathologists.  April, 2010.