PMLBCL : Immunophenotype

Comments:
Primary Mediastinal Large B-cell Lymphoma (PMLBCL) - Immunophenotype: PMLBCL expresses pan B-cell antigens CD19, CD20, CD22, and CD79a. Despite functional Ig gene arrangements and the presence of CD79a, most cases lack surface or cytoplasmic immunoglobulin. Surface Ig may be present on flow cytometry in a small subset of cases.

The status of other markers is as follows: PAX5+; CD30+ in 70% of cases with weak and heterogenous staining; CD15+ in minority of cases; EBV absent; IRF4/MUM1+ in 75%; BCL2+ in 55-80%; BCL6+ in 60%; CD10+ in 25%; CD11c+ in 40%; CD21 negative; CD23+ in 70%; PDL1+, PDL2 (CD273)+ in 72%; MYC+ in >30% of cells.

MAL gene on chromosome 2q - a marker associated with thymic medullary B-cells - is expressed in 70% of PMLBCL but only 3% of diffuse large B-cell lymphomas. It can be detected by molecular techniques or immunohistochemistry.

Transcription factors PU.1, OCT2, PAX5, and BOB1 are often positive in a majority of cases.

Image courtesy of: Lorand Kis, MD, Sweden; used with permission.