Morphological features and CN comparison of t(14;18)⁻FL BCL6-break positive vs BCL6-break negative cases. (A-H) Case FL5, group A2. (A) Axillary LN with effaced architecture by an atypical lymphoid infiltration with follicular growth pattern. The follicles are back to back without well-defined mantle zones (hematoxylin and eosin [H&E] stain; original magnification, ×50). (B) Higher magnification demonstrates that the infiltrate is mainly composed of centrocytes with a few scattered centroblasts (H&E stain; original magnification, ×400). (C) The tumor cells are CD20⁺ (immunoperoxidase, original magnification, ×50). (D) BCL2 is negative in the tumor cells but positive in the residual mantle zones and reactive T cells. (E) The tumor cells are BCL6⁺. FISH analysis using a BCL6 break-apart assay (inset) shows a signal constellation of 1 colocalized signal (yellow arrow) and 1 split signal (red and green arrows) consistent with gene rearrangement. Tumor cells are CD10⁺ (F), whereas the residual follicular dendritic cells are CD23⁺ (G). Note that the tumor cells are CD23⁻. (H) MIB1 shows a low proliferation rate without polarization in the germinal centers (D-H; immunoperoxidase; original magnification, ×100). (I) Comparative plot of CN and CNN-LOH between 9 BCL6 break positive cases and 35 BCL6 break negative cases. The only significantly different region is indicated in the plot, and the color denotes the enriched group (Fisher’s exact test; adjusted P < .05; minimum 3 cases).