ABSTRACT
<p><b>OBJECTIVE</b>To study the expression of MUM-1/IRF4 and its significance in follicular lymphoma.</p><p><b>METHODS</b>Ninety-eight cases of follicular lymphoma were enrolled into the study. They were graded according to the 2008 WHO criteria. The expression of MUM-1/IRF4 protein and other markers (CD10, bcl-6, bcl-2 and Ki-67) was studied using tissue microarray and immunohistochemistry.</p><p><b>RESULTS</b>Amongst the 98 cases studied, there were 24 grade 1 cases, 30 grade 2 cases, 26 grade 3A cases and 18 were grade 3B cases. The rates of expression of MUM-1/IRF4, CD10, bcl-6, bcl-2 and Ki-67 (≥ 25%) were 39.8% (39/98), 62.2% (61/98), 80.6% (79/98), 87.8% (86/98) and 50.0% (49/98), respectively. MUM-1/IRF4 predominantly expressed in high-grade follicular lymphoma and showed a significantly positive correlation with lymphoma grade (r = 0.628, P = 0.000) and Ki-67 index (r = 0.473, P = 0.000). MUM-1/IRF4 expression had a significantly negative correlation with CD10 expression (r = -0.597, P = 0.000), but no correlation with bcl-6 and bcl-2 expression.</p><p><b>CONCLUSIONS</b>MUM-1/IRF4 expression is significantly higher in high-grade follicular lymphoma, indicating that these cases have a high proliferative activity, more aggressive behavior and poorer prognosis. MUM-1/IRF4, when strongly expressed, is another helpful marker for the diagnosis of high-grade follicular lymphoma.</p>