CD23 expression in transformed small lymphocytic lymphomas/chronic lymphocytic leukemias and blastic transformations of mantle cell lymphoma.

The immunophenotypic marker, CD23, has been shown to be a useful marker for the distinction of small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) from mantle cell lymphoma (MCL). The usefulness of this marker has not previously been analyzed in distinguishing various "large cell" transformations of SLL/CLL from blastic transformations of MCL (MCL-B). Thirteen cases of transformed SLL/CLL and six cases of MCL-B were analyzed for expression of CD23, either by flow cytometry of peripheral blood, bone marrow, or fresh tissue or by immunoperoxidase staining of paraffin-embedded archival tissue. All of the 13 cases of transformed SLL/ CLL expressed CD23 and all of the 6 cases of MCL-B were negative for CD23. Therefore, CD23 is retained in transformed SLL/CLL. It is a useful marker in distinguishing transformed SLL/CLL from MCL-B and thus might aid in distinguishing those cases that present de novo without a previous diagnosis of SLL/CLL or MCL.