[1407] CD23(+) Follicular Lymphoma: Immunophenotypic and Clinical Features

H Olteanu, AM Harrington, SH Kroft. Medical College of Wisconsin, Milwaukee, WI

Background: Follicular lymphoma (FL) is typically a CD10(+)/CD5(-)/FMC-7(+) B cell lymphoma with variable CD23 expression. Occasional FL cases are CD23(-), although the clinical significance of this finding is uncertain. CD23 positivity by immunohistochemistry (IHC) has been recently linked to specific anatomic sites (inguinal region)(Thorns et al. Histopathology 2007) or to cases with diffuse growth pattern and specific chromosomal alterations (Katzenberger et al. Blood 2009). We studied the expression of CD23 by flow cytometry and correlated CD23 expression with pathologic and clinical parameters.
Design: Lymph node (LN) biopsies from 58 consecutive FL cases were evaluated by four-color flow cytometry with antibodies against CD5, CD10, CD19, CD20, CD23, CD38, FMC-7, kappa and lambda. Expression of CD23 was assessed in the neoplastic cells based on an isotype control threshold. Clinical data were available from chart review.
Results: The patient cohort consisted of 33 men and 25 women, with a mean age of 58 years (median follow-up, 34 months). There were 29 grade I, 10 grade II, and 19 grade III FLs. 19/58 cases (32%) were negative for CD23. Of these, 6 were grade I, 2 were grade II and 11 were grade III cases. Grade III FLs were CD23(-) significantly more often (11/19, 58%) than grade I and II cases combined (8/39, 21%)(p=0.007). Inguinal LNs had a higher proportion of CD23(+) FLs compared to other sites: 16/18 (89%) vs. 23/40 (58%) (p=0.032). The other immunophenotypic findings were similar between CD23(+) and CD23(-) patients. There was no correlation between CD23 expression and the age, sex, stage of disease, bone marrow involvement, growth pattern or cytogenetic findings. Of the CD23(+) cases, the median percentage of cells expressing CD23 was similar in the inguinal FLs vs. other sites (63% vs. 60%, p=0.887). The median event-free survival (EFS), calculated from FL diagnosis to treatment failure, was 96 months in the CD23(+) group and 16 months in the CD23(-) FLs (p=0.001, log rank Mantel-Cox test).
Conclusions: Our study shows that grade III FLs are more often CD23(-) than grade I and II cases. Similar to a previous IHC study, we found that FLs in inguinal LNs are more frequently CD23(+) than in LNs from other sites. The proportion of CD23(+) FLs as estimated by flow cytometry was higher in our patients than that estimated by IHC by Thorns et al. (68% of all FLs / 89% of inguinal FLs vs. 27% / 38%, respectively). The EFS is significantly lower in the CD23(-) FLs, although this may reflect the higher number of grade III FLs in this group.
Category: Hematopathology

Monday, March 22, 2010 1:00 PM

Poster Session II # 161, Monday Afternoon

 

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