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.

Immunohistochemical Expression Pattern

CD3	Negative
CD5	Negative (rare + cases)
CD10	Negative
CD20	Positive
CD23	Negative
CD43	Negative
CD103	Flow Marker – Usually negative
AnnexinA1	Negative: + in Hairy Cell Leukemia
Cyclin D1	Negative
Ki-67	Targetoid pattern with increased positivity in the germinal centers and marginal zone areas.
Bcl-6	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

Parker, A., et. al. “Best Practice in Lymphoma Diagnosis and Reporting.” British Committee for Standards in Haematology, Royal College of Pathologists. April, 2010.