DISTINCTION BETWEEN SMALL LYMPHOCYTIC AND MANTLE CELL LYMPHOMA BY IMMUNOREACTIVITY FOR CD23

Immunoreactivity for CD23, a B-cell activation antigen, was compared i n 22 cases of B-cell small lymphocytic lymphoma (SLL)/ chronic lymphoc ytic leukemia (CLL) and 15 cases of mantle cell lymphoma (MCL) (interm ediate lymphocytic lymphoma or centrocytic lymphoma) to determine if t he presence of this antigen can be used as a criterion to distinguish between these two low-grade B-cell lymphoproliferative processes. CD23 immunoreactivity was observed in 21 of 22 cases (95%) of SLL/CLL, whe reas only 2 of 15 cases (13%) of MCL were reactive for this antigen; t herefore, lack of CD23 reactivity is statistically significantly assoc iated with MCL (P < 0.0001). In addition, lack of CD23 immunoreactivit y is also statistically significantly associated with SLL with plasmac ytoid differentiation in comparison with typical SLL (P < 0.0003), alt hough only a small number of cases were evaluated. SLL/CLL, MCL, and S LL with plasmacytoid differentiation cases were all uniformly immunore active for pan-B-cell antigens such as CD20 and CD22. Immunoreactivity for CD23 appears to be a useful marker to aid in distinguishing SLL/C LL from MCL and may be helpful in routine immunophenotypic screening o f low-grade B-cell derived lymphoproliferative processes.