Identification of dominant T-cell receptor clonotypes from stored tissue biopsy specimens. (A) The number of dominant clonotypes of TCRγ (mustard) and TCRβ (lavender) identified in both baseline FFPE and serum samples from 18 patients who had at least 1 dominant TCR clonotype identified from baseline FFPE tissue. Of the 18, 16 had matched serum samples, with a dominant clonotype detected in 15. Thirteen dominant TCR clonotypes (lime green) across 7 of those 15 patients were identified in serum that were not identified in FFPE samples. (B) The number of dominant TCRγ (mustard) and TCRβ (lavender) clonotypes detected in baseline serum in 16 patients without available baseline FFPE samples. (C) Tissue source of all dominant TCR clonotypes detected exclusively in FFPE and serum samples, as well as those detected in both tissue sources. (D) The median number and range of clonotypes identified in baseline tissue samples across histologic subtypes of PTCL. ALK⁻ ALCL, ALK− negative ALCL; EATL, enteropathy associated T-cell lymphoma; HSTCL-gd, hepatosplenic T-cell lymphoma gamma delta; PCGDTCL, primary cutaneous gamma delta T-cell lymphoma; PTCL-NOS-L, lymphoepithelioid cell variant of PTCL-NOS; PTCL-TFH, PTCL-T-follicular helper phenotype; SPLTCL, subcutaneous panniculitislike T-cell lymphoma.