Angioimmunoblastic T-cell Lymphoma of Cytotoxic T-cell Phenotype Containing a Large B-cell Proliferation With an Undersized B-cell Clonal Product

Angioimmunoblastic T-cell lymphoma is a nodal peripheral T-cell lymphoma considered to be derived from CD4(+) follicular helper T cells. It is characterized by the proliferation of arborizing vessels, hyperplastic follicular dendritic cells, and a polymorphous lymphoid infiltrate including large B immuno-blasts, which could be polyclonal, oligoclonal, or monoclonal. The polymerase chain reaction-based clonality study of lympho-proliferations is increasingly popular in the diagnostic workup. With the commercially available Biomed-2 protocols, lympho-proliferations with amplicons in the expected size ranges are considered clonal, whereas clonal products outside the expected ranges are extremely rare. We presented the case of a 60-year-old male patient with angioimmunoblastic T-cell lymphoma, in which the neoplastic T cells expressed CD8, bcl-6, and programmed death-1. Furthermore, there was a proliferation of large B cells in this tumor. The results of T-cell receptor gene rearrangement study using the Biomed-2 protocols showed clonal rearrangement with amplicons falling within the expected size ranges. Interestingly, the size of the amplicons detected by the Biomed-2 immunoglobulin heavy chain gene (IgH) rearrangement using FR2/JH primers was around 240 bp, slightly smaller than the expected size ranges. Through cloning, sequencing, and BLAST searches, we confirmed that the FR2/JH amplicon was derived from the IgH rearrangement with a deletion of a short segment. Our case illustrates that polymerase chain reaction amplicons outside the expected size ranges may still be clonal products.