Immunohistochemistry (IHC) and immunofluorescence (IF) of low-grade follicular lymphoma showing BMI-1low/EZH2− neoplastic centrocytes and BMI-1low/EZH2+ centroblasts.
(A-B, first row) IHC on reactive follicle with BMI-1 (A) and EHZ2 (B). Note that macrophages are BMI-1+ (MΦ) and EZH2−, centrocytes (cc) are BMI-1+ and EHZ2−, whereas centroblasts (cb) are BMI-1−but EZH2+. M, mantle cells (BMI-1+EZH2−); DZ, dark zone; LZ, light zone. Original magnification, 20× objective. (C-D, second row) IHC on low-grade follicular lymphoma. (C) Reactive centrocytes mainly on the left and neoplastic centrocytes mainly on the right side of the image (arrows). Reactive centrocytes are clearly BMI-1+, whereas neoplastic (larger) centrocytes are weakly positive and negative. (D) Residual germinal center overrun by neoplastic centrocytes. Residual centroblasts are EZH2+. Original magnification, 20× objective. (E-F, third row) IHC on low-grade follicular lymphoma (detail) showing Mib-1/Ki-67+ neoplastic centroblasts (E) and, with similar magnification, EZH2+ centroblasts (F). Original magnification, 63× objective. All photographs are from a representative experiment with one low-grade follicular lymphoma (Berard grade I/II).
