Comparison of Follicular Helper T-Cell Markers with the Expression of the Follicular Homing Marker CXCR5 in Peripheral T-Cell Lymphomas-A Reappraisal of Follicular Helper T-Cell Lymphomas.

Peripheral T-cell lymphomas (PTCLs) expressing multiple follicular T helper (TFH) cell-related antigens are now classified as TFH lymphomas (TFHL), including angioimmunoblastic, follicular, and not otherwise specified (NOS) types. CXCR5 is the TFH cell-defining chemokine receptor that, together with its ligand CXCL13, plays a critical role in the development of follicles and the positioning of TFH and B cells within follicles. A comprehensive immunomorphologic study was performed to investigate the expression pattern of CXCR5 in a large cohort of nodal PTCLs, particularly those with a TFH cell phenotype, and to compare its expression with six other TFH cell-related antigens. We found that CXCR5 is widely expressed in neoplastic TFH cells, except in TFHL-NOS, and represents a specific marker of this lymphoma entity. Our results suggest that CXCR5 directs the distribution of neoplastic T cells in the affected lymph nodes and may influence the formation of the pathognomic pathological FDC network.