[1232] CD20-Positive Multiple Myeloma: A Subtype Associated with a Worse Prognostic Profile
S Kitahara, A Yung, R Alsabeh. Cedars-Sinai Medical Center, Los Angeles, CA
Background: CD20 positivity has been reported in 13-22% of patients with multiple myeloma (MM). The exact clinical significance of CD20 expression in MM is not clear, however, this subset is of interest because these patients may benefit from rituximab therapy. Some studies suggest that CD20-expressing MM reflects a more aggressive MM subtype. However, recent studies have demonstrated a correlation between CD20 and a favorable prognostic marker t(11;14). The aim of this study is to describe the relationship between CD20 and genetic abnormalities detected by conventional karyotype analysis and/or fluorescent in situ hybridization (FISH), and to explore the prognostic implication of CD20 expression.
Design: 50 cases of MM from 2002 to 2008 with genetic information (conventional karyotype on 49 cases and/or FISH for deletion (del) of 13q) on 18 cases) were evaluated for expression of CD20, PAX-5, bcl-1, p53 and CD56 by immunohistochemistry.
Results:
| CD20-positive (n=8) | CD20-negative (n=42) | | % CD20 (+) MM cells | 20 - 100 | - | | % MM cells/biopsy (mean) | 84 | 44 | | Plasmablastic morphology | 2 (25%) | 11 (26%) | | PAX-5 (+) | 1 (13%) | 1 (2%)* | | bcl-1 (+) | 7 (88%) | 7 (17%) | | p53 (+) | 2 (25%) | 8 (19%) | | CD56 (-) | 4 (50%) | 11 (26%) | | Deletion of 13q (FISH) | 3/5 (60%) | 1/13 (8%) | | Abnormal karyotype | 1/7 (14%) | 12 (29%) | | Translocations involving chromosome 14 | 1/7 (14%) | 3 (7%) | | Hyperdiploid | 0/7 (0%) | 3 (7%) | * - weak staining
Conclusions: CD20 expression is seen in 16% (8 of 50) of MM cases and the majority (7 of 8) are associated with diffuse bcl-1 expression. When expressed, CD20-positivity is seen in 20-100% of myeloma cells, and can potentially be a good target for rituximab therapy. CD20-positive MM is associated with a higher tumor burden in bone marrow biopsies and more commonly demonstrates adverse prognostic features, such as del(13q) and negative expression of CD56. Hyperdiploid DNA content, indicative of a good prognosis, was not present in any of the CD20-positive MM. CD20-expression assessment may be useful in evaluating MM.
Category: Hematopathology
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 202, Wednesday Morning
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