Abstract
The distinction of de novo diffuse large B-cell lymphomas (DLBCL) from transformed MALT lymphomas is difficult in the absence of MALT-component. This study aims to study the phenotypic expression profiles of extranodal lymphomas, focusing on the characteristics of high-grade tumors. We categorized 52 extranodal B-cell lymphomas into Grade 1 (low-grade MALT lymphoma), Grade 2 (DLBCL with MALT component), and Grade 3 (DLBCL without MALT component) tumors based on histomorphology. There were 26 (50%) Grade 1, 9 (17%) Grade 2, 15 (29%) Grade 3 tumors. We could not assess the grade of two tumors (4%) due to limiting tumor tissues. The expression of CD10, Bcl-2, Bcl-6, and p53 was also investigated by immunohistochemistry. CD10 expression was present in one Grade 1 and six Grade 3 tumors. Bcl-6 expression was more common in high-grade tumors (p=0.001), while Bcl-2 expression was associated with lower-grade tumors (p=0.001). CD10 expression was more useful as a marker in distinguishing Grade 2 from Grade 3 tumors than Bcl-6 expression. p53 was more frequently expressed in high-grade tumors; the higher frequency of p53 expression in Grade 2 tumors may suggest a potential role in the transformation of Grade 1 to Grade 2 tumors.
