- Positive: CD79a, focal CD20 and
- Negative: CD5, BCL1, BCL6 and
- ISH: Kappa restriction.
- The lymph node architecture is
effaced by nodular proliferation of small lymphocytes. The tumor
cells have slightly irregular nuclei with occasional small
nucleolus. The major differential diagnosis includes follicular
lymphoma, mantle cell lymphoma, and nodal marginal zone lymphoma.
The cytologic features and lack of BCL6 and CD10 expression are
against follicular lymphoma. The negative BCL1 staining is
also against mantle cell lymphoma. Overall, a nodal marginal zone
lymphoma is favored.