756 | REAL‐WORLD STUDY OF GOLIDOCITINIB FOR THE TREATMENT OF RELAPSED OR REFRACTORY PERIPHERAL T CELL LYMPHOMA: RETROSPECTIVE DATA FROM MEDICAL CENTERS IN CHINA

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Introduction: Diagnosing T-cell lymphoma (T-NHL) is often challenging due to phenotypic overlap with reactive T-cells.Antibodies targeting the two mutually exclusive isoforms of the constant TCR β-chain, TRBC1 and TRBC2, provide a unique opportunity to assess clonality, given that reactive T cells exhibit a TRBC biphasic pattern.Literature suggests that TRBC1 below 15% or above 85% or TRBC2:TRBC1 ratio < 0.18 or > 5.7 may indicate phenotypic TCRαβ clonality.Methods: We evaluated a flow cytometry (FC) panel including CD2, CD3, CD45, CD7, CD5, CD8, CD4, CD10, CD26, CD56, PD1, TCRαβ, TCRγδ, TRBC1, and TRBC2.Samples were processed using a stain-lyse-wash protocol and 200000 events were recorded per sample.Results: From March 2024 to February 2025 we prospectively analyzed 27 samples (14 peripheral blood [PB], 7 bone marrow [BM], and 6 lymph node biopsies [LN]).The case series included 12 T-NHL at diagnosis (2 T-NHL NOS, 1 AITL, 3 T-LGL leukemia, 1 T-PLL, 1 T-ALL, 2 Sézary syndrome [SS], 2 Mycosis Fungoides [MF]), 2 T-NHL BM after therapy and 13 non-T-NHL cases (3 DLBCL, 1 NLPHL, 1 thymoma, 1 mononucleosis, 5 reactive hyperplasia, 2 healthy controls).In non-T-NHL group and in two PB MF samples no aberrant phenotypes and polytypic ratio were observed (median CD4þ TRBC ratio 1.0, range 0.03-1.7;median CD8þ TRBC ratio 1.9, range 0.5-3.1).In contrast, all 10 T-NHL displayed a T-cell cluster with a monotypic restriction (TRBC1-restricted in 4/10, median 0.05, range 0.002-0.13;TRBC2-restricted in 6/10, median 594, range 21.3-3179).Case-specific findings included an aberrant CD3þ CD4þ CD7-CD5þ PD1þ CD10þ/-TRBC1þ cluster in AITL with BM involvement (Figure 1).LN biopsy from a T-NHL NOS showed a CD3þ CD4-CD8þdim CD7þ/-and CD5þ/-TRBC2þ cluster.A relapsed T-NHL NOS with leukemic presentation exhibited three distinct subclones within a CD3þ CD7þ population: a larger CD8þ CD4-and two smaller CD4þ CD8-and CD4þ CD8þ clones, all TRBC1 restricted.Intracytoplasmic TRBC2 monotypy was detected in CyCD3þ CD4þ CD8þ CD1aþ blast cells in a cortical T-ALL in PB.The T-PLL showed a CD3þ CD4þþ CD7þ CD8-CD56-TRBC1þ phenotype in BM.SS showed classic CD3þ CD4þ CD5þ CD7-CD26-phenotypes, TRBC1þ in one and TRBC2þ in other.Three cases of T-LGL leukemia showed the following phenotypes: CD3þ CD8þlow CD4-CD7-CD5þ/-CD56-TRBC2þ, CD3þ CD4þ CD8þ CD56-TRBC2þ, and CD3þ CD8þ CD5þ CD7-CD56þ TRBC2þ, respectively.Phenotypic evaluation in two BM samples after therapy revealed a polytypic CD4þ ratio (1.5) in an AITL case, while a T-NHL NOS case showed persistent disease (CD3þ CD4þ CD8-CD5low CD7-TRBC2þ ratio 81.6), corroborated by molecular and histochemical analysis.Molecular TCR gene rearrangement was available in 13 cases, demonstrating full concordance with FC findings.Conclusions: TRBC monotypy by FC provides a rapid diagnostic method to detect clonal T-cells for T-NHL screening.However, further large-scale studies are needed to validate diagnostic accuracy.

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