AITL : Immunophenotype - BCL6
Immunophenotype of Angioimmunoblastic T-cell Lymphoma (AITL): CD10 positivity (heterogenous, weak) is seen in a small number of T-cells (clear cells on H&E) in 80% to 90% of cases. BCL6 is often coexpressed (shown here). There is expression of CXCL13 in the majority of tumor cells in almost 90% of cases. The expression of these 3 markers (CD10, BCL6, & CXCL13) is an important clue to the diagnosis of AITL and further supports helper T-cell origin. The neoplastic T cells also express inducible costimulatory (ICOS) and programmed death 1 (PD1) markers. No single marker is diagnostic of AITL. In general, PD1 and ICOS are more sensitive but CXCL13, CD10, and BCL6 are more specific for the diagnosis of AITL. The neoplastic cells should express at least 3 of these markers to prove their helper T-cell derivation.