Figure 5

Gross and histopathology of lymphoid tissues of strain BCL2⁺IL6⁺AID⁻ mice. (a) Necropsy photographs of a representative disease-bearing mouse that contained multiple Peyer’s patches at different stages of malignant development (left). Spleen (SPL) and mesenteric lymph node (MLN) of the same mouse were grossly enlarged (right). In some cases, MLNs reached weights of 3 grams. (b) Low-power photomicrographs of immunolabeled FFPE tissue sections of Peyer’s patches at an early (top and center panels) or more advanced (bottom panel) stage of disease progression. Increased B220⁺ follicles (top) contain highly proliferative Ki67⁺ B cells (center), whereas interfollicular areas harbor large numbers of CD138⁺ lymphoplasmacytic cells (bottom). In some moribund mice, enlarged Peyer’s patches seemed to be the underlying reason for intestinal obstructions and intussusceptions.