Soft Tissue, Small lymphocytic lymphoma/Chronic lymphocytic leukemia, CD20 stain

Small lymphocytic lymphoma (SLL) and Chronic lymphocytic leukemia (CLL) are essentially synonymous terms for a B cell neoplasm that shows aberrant CD5, CD23 expression. B cell markers (CD19, CD20, PAX5) are expressed, although CD20 is generally dim on flow cytometry. Importantly, CD20 can be lost in response to anti-CD20 treatment (ex. rituximab, Rituxan®). Other B-cell markers are generally preserved, with CD19 and CD79A available for flow cytometry. CD79A and PAX5 are available for immunohistochemistry.

Histologically, there is diffuse effacement of architecture with proliferation centres, which are characteristic. Scattered proliferation centres are seen in this specimen. As the name suggests, cells are small lymphocytes with clumped chromatin, with usually round nuclei. Mitotic activity/proliferation index are generally low (10% in this case).

This slide shows CD20 stain. H&E stain and immunohistochemistry for CD5 and CD23 are included in the Related Content section. The case was negative for Cyclin D1, CD10, BCL6 and CD30 (not shown).