Secondary Lymphoid Tissues ›› Spleen ›› Normal Normal Spleen* Click Here for Full Size Additional Image 1 Additional Image 2 › Microscopic Features: Spleen is divided into 2 main zones: Red pulp and white pulp The white pulp contains the lymphoid cells and appears as small blue/purple aggregates of lymphoid tissue The red pulp contains the sinusoids along with scattered hematopoietic cells and appears red in the image above › Normal % blood-PB, marrow-BM, lymphoid tissue-LN: PB: N/A BM: N/A LN: N/A › May Resemble: Normal Lymph Node Normal Mucosa Associated Lymphoid Tissue (MALT) › Differential Diagnoses: Reactive lymphoid hyperplasia Infection Splenic Marginal Zone Lymphoma Hairy Cell Leukemia Follicular Lymphoma › Classic Immunophenotype: "T"-cells have the "Tiny" CDs: CD2, CD3, CD4, CD5, CD7, CD8 "B"-cells have the "Bigger" CDs: CD19, CD20, CD22 › Misc: In Splenic Marginal Zone Lymphoma, the neoplastic cells involve the white pulp area of the Spleen (as opposed to Hairy Cell Leukemia which involves the red pulp area)