B-cell lymphomas.

(A) Small B-cell lymphoma. A uniform population of small, mature, round lymphocytes within an expanded white pulp with similar cells invading the red pulp (H&E, × 750). (B) Splenic marginal zone lymphoma. Widening of the marginal zone with medium-sized B cells containing prominent eosinophilic cytoplasm with no red pulp infiltration (H&E, × 400). (C) Advanced SMZL. Evidenced by invasion of the red pulp and compression of the white pulp (H&E, × 400). (D) Advanced SMZL. Centroblastlike cells with mitotic figures obliterating normal architecture. Cytoplasm is moderately extensive (H&E, × 750). (E) Follicular B-cell lymphoma. The pale zone represents loss of small dark lymphocytes in both the periarteriolar lymphoid sheath (PALS) and follicle and replacement with mixed centrocytes and centroblasts (H&E, × 150). (F) Follicular B-cell lymphoma. Mixed population of large centroblasts, cleaved centrocytes, and small lymphocytes with few immunoblasts (H&E, × 750).