T(11;14), Cyclin D1, CD20 and CD56 in Multiple Myeloma: A Retrospective Study of Pathologic and Clinical Associations
Authors: Szabo Agoston Gyula , Gang Anne Ortved , Poulsen Tim Svenstrup , Klausen Tobias Wirenfeldt , Nørgaard Peter H. 
Published: October 2019

Abstract
Abstract 4983

Background:
Multiple Myeloma (MM) can be stratified prognostically according to specific genetic aberrations, one of which is t(11;14), a marker of good risk. Subgroups of MM may also be defined based on specific immunophenotypes, such as Cyclin D1+, CD20+ and CD56- MM. Although the literature of immunophenotypic correlates of MM produced diverging results, the Cyclin D1+, the CD20+ and the CD56- phenotypes have all previously been found to be associated with t(11;14). Based on results showing strong associations, it was hypothesized that Cyclin D1 and CD20 could be used as surrogate markers for t(11;14). CD20 expression is an aberrant feature of MM, creating potential diagnostic difficulty in daily pathology routine in the differentiation from non-Hodgkin's B-cell lymphoma with plasmacytic morphology. Moreover, CD20 is the target of Rituximab, which is widely used in the treatment of non-Hodgkin's lymphoma.

Purpose:
We conducted a retrospective study to evaluate the prevalence of t(11;14), Cyclin D1, CD20 and CD56 expression in primary MM, and to examine their previously reported associations. Secondly, we wanted to assess, whether the studied pathologic features were associated with clinical characteristics, and thirdly, whether they were predictive factors for response to primary treatment.

Material and methods:
Bone marrow aspirates from 126 patients diagnosed with MM from 2004–2010 were examined retrospectively. Tissue microarrays (TMAs) were constructed from formalin fixed, paraffin embedded samples. 4 cores of 1mm were used per patient. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were carried out with commercially available reagents. Plasma cells were identified with anti-CD138 IHC. Clinical data were obtained from the Danish Multiple Myeloma Database. Patients who received primary treatment (n=96) were examined separately based on whether they were treated with high-dose therapy (HDT). Response rates were evaluated after concluded primary treatment. Chi-square test and Fisher's exact test were used for all calculations.

Results:
The TMAs yielded sufficient material for assessment in 110 (87 %) to 122 (97 %) of 126 patients. t(11;14), Cyclin D1, CD20 and CD56 expression were found in 16 %, 43 %, 16 % and 73 % of patients, respectively. t(11;14) was associated with Cyclin D1+ (p<0. 01), CD20+ (p=0. 01) and CD56-(p<0. 01) myeloma. However, t(11;14) was only found in 39 % of CD20+, 37 % of Cyclin D1+ and 37 % of CD56- patients. Cyclin D1+ patients presented more often with anemia (p=0. 03), hypercalcemia (p=0. 02), and high bone marrow infiltration (p=0. 02). CD56- patients presented more often with anemia (p=0. 05) and hypercalcemia (p=0. 01). We examined Cyclin D1+ patients with and without the presence of t(11;14), and found no difference in their clinical characteristics. None of the assessed pathologic features were associated with specific response rates to primary treatment.

Discussion and conclusion:
TMA was an effective method of assessing bone marrow aspirates with MM infiltrates despite an inherent variability in tissue density throughout the paraffin block. The prevalence of t(11;14), Cyclin D1, CD20 and CD56 expression in MM were in accordance with previously published findings. t(11;14) was associated with Cyclin D1+, CD20+ and CD56- myeloma, but Cyclin D1 and CD20 expression were not suitable as surrogate markers for t(11;14). The Cyclin D1+ and CD56- phenotypes were associated with adverse clinical characteristics at diagnosis. None of the assessed pathologic features predicted response to primary treatment.

Disclosures:
No relevant conflicts of interest to declare.