SMZL : Differential Diagnosis

Comments:
Splenic Marginal Zone Lymphoma (SMZL) - Differential Diagnosis: The differential diagnosis of SMZL includes the following entities (along with helpful distinguishing features).

Follicular Lymphoma: CD10+ve, BCL6+, and t(14;18)(q23;q32).

Mantle Cell Lymphoma: CD5+ve, cyclin D1+ve and shows t(11;14)(q13;q32).

Hairy Cell Leukemia: positive for CD11c, CD25, CD103, CD123, TRAP, BRAF V600E, and Annexin A1.

Lymphoplasmacytic Lymphoma (LPL): About 25%-30% of SMZL show plasmacytic differentiation with serum paraproteinemia and may be difficult to distinguish from LPL. Features favoring SMZL over LPL include del 7q, tumor micronodules in splenic white pulp, intrasinuoidal pattern of bone marrow involvement, and IgD expression by tumor cells. Serum IgM levels in SMZL rarely reach the level to cause hyperviscosity syndrome. LPL shows subtle and diffuse involvement of bone marrow instead of intrasinusoidal lymphoid aggregates. In splenectomy specimens, LPL shows diffuse red pulp involvement. The presence of MYD88 L265P mutation favors LPL.

MALTOMA: Sometimes, MALT-type MZL involves spleen in a marginal zone pattern and produces tumor micronodules grossly. Features favoring SMZL include presence of del 7q, absence of t(11;18), and expression of IgD.

The image shows marginal zone compartment in a SMZL. The cells have slightly irregular enlarged nuclei and moderate to abundant pale cytoplasm. Scattered large B-cell resembling centroblasts or immunoblasts are also present.