Massive hyperplasia of marginal zone B-cells with clear cytoplasm in the lymph node: a case report

An enlarged axillary lymph node from a 63-year-old woman showed proliferating marginal zone B-cells arranged in a vague nodular pattern or in band-forming aggregates throughout the cortex. Marginal zone B-cells, which also infiltrated the adjacent fatty tissue, had round or slightly indented nuclei of medium size and a moderate amount of clear cytoplasm. Immunohistochemically, these cells were CD20+, CD79a+, Bcl-2+, sIgD-, CD5-, CD10-, CD21-, CD23-, CD45RO-, Bcl-6-, and cyclin D-. A portion of the cells were sIgM- and CD43-positive. The polytypic nature of these cells was demonstrated by immunohistochemistry and polymerase chain reaction. Systemic bacterial infection appears to be the cause of marginal zone B-cell hyperplasia. This unusual marginal zone B-cell hyperplasia should be differentiated from low-grade B cell lymphomas, and particularly from nodal marginal zone B-cell lymphomas.