case_images: PMC8182221_01
case_images: Hematoxylin-eosin-stained slide of the subcortical hypocellular bone marrow showing
  small non-paratrabecular aggregates and scattered interstitial cells (50x oil).
case_images: 10.1177_23247096211021228-fig1.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig1.jpg
case_images: fig1-23247096211021228
case_images: Lymphoid aggregates were composed of CD20 positive B cells with admixed CD138 positive plasma cells with kappa predominance (Figures 1-6).
case_images: Immunohistochemistry for CD20 shows that the majority of the cells within the aggregate
  and many within the interstitium are B cells (20x).
case_images: 10.1177_23247096211021228-fig2.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig2.jpg
case_images: fig2-23247096211021228
case_images: Lymphoid aggregates were composed of CD20 positive B cells with admixed CD138 positive plasma cells with kappa predominance (Figures 1-6).
case_images: Conversely, CD3 immunohistochemistry shows only occasional scattered T cells (20x).
case_images: 10.1177_23247096211021228-fig3.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig3.jpg
case_images: fig3-23247096211021228
case_images: Lymphoid aggregates were composed of CD20 positive B cells with admixed CD138 positive plasma cells with kappa predominance (Figures 1-6).
case_images: CD138 demonstrates increased numbers of plasma cells within the interstitium and the
  aggregate.
case_images: 10.1177_23247096211021228-fig4.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig4.jpg
case_images: fig4-23247096211021228
case_images: Lymphoid aggregates were composed of CD20 positive B cells with admixed CD138 positive plasma cells with kappa predominance (Figures 1-6).
case_images: The plasmacytoid lymphocytes and plasma cells are kappa restricted.
case_images: 10.1177_23247096211021228-fig5.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig5.jpg
case_images: fig5-23247096211021228
case_images: Lymphoid aggregates were composed of CD20 positive B cells with admixed CD138 positive plasma cells with kappa predominance (Figures 1-6).
case_images: The histograms represent the gated lymphocytes. Of the gated lymphocytes, approximately
  34% (red dots) are B cells that coexpress CD19 and CD20 and exhibit surface kappa light
  chain restriction.
case_images: 10.1177_23247096211021228-fig6.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig6.jpg
case_images: fig6-23247096211021228
case_images: Lymphoid aggregates were composed of CD20 positive B cells with admixed CD138 positive plasma cells with kappa predominance (Figures 1-6).
case_images: Magnetic resonance imaging of the brain showing intracranial white matter enhancements
  consistent with disease progression (blue arrows).
case_images: 10.1177_23247096211021228-fig7.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig7.jpg
case_images: fig7-23247096211021228
case_images: A repeat MRI was done that showed progression of white matter enhancement (Figure 7).
case_images: Magnetic resonance imaging of the brain 2 months after treatment with ibrutinib showing
  complete resolution of previously noticed white matter enhancements.
case_images: 10.1177_23247096211021228-fig8.jpg
case_images: PMC8182221_01_10.1177_23247096211021228-fig8.jpg
case_images: fig8-23247096211021228
case_images: Repeat MRI brain after 2 months of ibrutinib showed complete resolution of intracranial enhancement (Figure 8).