Extra-Nodal Marginal Zone Lymphoma of Mucosa-Associated Lymphoid Tissue

Siba El Hussein, MD
2 min readOct 23, 2022

Lessons From the Friday Unknowns

Routinely-stained histologic sections show irregular fragments of tissue diffusely infiltrated by lymphoma.

The lymphoma is composed of small to intermediate-sized lymphoid cells with irregular nuclear contours, mature chromatin, inconspicuous nucleoli and variable amounts of clear cytoplasm (“monocytoid” morphology). A few lymphoma cells show plasmacytoid appearance with eosinophilic cytoplasm and eccentric nuclei. Few scattered plasma cells are seen. No diffuse sheets of large cells or areas of necrosis are observed.

The neoplastic cells are positive for CD5, CD20 and BCL2. The neoplastic cells are negative for CD3, CD10, CD21, CD23, CD43, BCL6, cyclin D1, LEF1 and SOX11. CD138 highlights rare scattered plasma cells. Kappa in situ hybridization highlights a subset lymphoma cells with plasmacytic differentiation, as well as plasma cells, in a kappa-monotypic pattern. Lambda in situ hybridization is negative. The proliferation index measured by Ki-67 is <5% in the neoplastic cells.

A concurrent flow cytometry analysis performed on cell suspension show an aberrant B-cell population positive for CD5, CD19, CD20, CD22, CD45 and kappa light chain restricted; the cells are negative for CD10 and lambda light chain.

This morphology and immunophenotype support the diagnosis of extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma).

Link to digital slides: https://bit.ly/3eSyhlz ~ Case 2

--

--

Siba El Hussein, MD

Hematopathology | Cytopathology | Molecular pathology | Digital pathology | Data science | Machine learning