PARR, which stands for PCR for Antigen Receptor Rearrangements, is used to discriminate between lymphoma/leukemia and reactive/inflammatory conditions when cytology is equivocal. Our canine PARR assay detects the expansion of B-cell cancer clones by amplifying the VJ region of the immunoglobulin heavy chain gene (IgH) and detects the expansion of T-cell cancer clones by amplifying a region in the T-cell receptor gamma chain gene.