Normal cell expression of CD20 is found on most B-cells (after CD19 and CD10 expression, before CD21/22 expression and surface immunoglobulin expression) and expression is retained on mature B-cells until plasma cell development, as well as ollicular dendritic cells. In diseased cells, there is positive staining on most B-cell lymphomas, come pre-acute B lymphoblastic leukemia/ lymphoblastic lymphoma (B-ALL/LBL); lymphocyte predominant Hodgkin lymphoma, dimly expressed in T-cells (benign and neoplastic), and spindle cell thymomas. Rixtuximab treated patients may lose CD20 positivity in B cell lymphomas.
- A formalin-fixed, paraffin-embedded (FFPE) tissue block is preferred specimen type
- One (1) unbaked, unstained slide for H&E staining (required) and two to three (2-3) positively charged unstained slides (all cut at 4-5 microns) for each test/antibody ordered
- Block and slide identifiers should be clearly written and match exactly with the specimen ID and specimen labeling as noted on the requisition.
Use cold pack for transport. Make sure cold pack is not in direct contact with specimen.