Clinicopathological features of adult T‐cell leukemia/lymphoma with T‐follicular helper phenotype

Abstract Aims T‐follicular helper (TFH) cells are effector T‐cells that are crucial for B‐cell selection and differentiation. T‐cell lymphomas derived from TFH cells have distinct characteristics. Additionally, in the World Health Organization (WHO) classification 5th edition, three lymphomas were introduced as independent disease entities with TFH cell origin. We aimed to investigate the clinicopathological features of adult T‐cell leukemia/lymphoma (ATLL) with a TFH phenotype (TFHP). Methods and Results We performed TFH immunohistochemistry analysis of five biomarkers for the biopsy specimen, with TFHP being indicated by a positive result for more than two markers. Among 75 cases of ATLL, 37.3% of them showed TFHP. Compared with cases of ATLL without TFHP, cases of ATLL with TFHP showed higher C‐reactive protein levels (p = 0.0219) and increased high endothelial venule proliferation (p = 0.024). However, there were no significant between‐group differences in overall survival as well as other clinical and morphological findings. Furthermore, there was no significant between‐group difference in TFH markers and FOXP3 expression. Conclusion Some patients with ATLL may present a TFHP, which should not preclude the diagnosis of ATLL. Although presenting a TFHP does not affect prognosis, it is important to identify cases of ATLL with a TFHP since it may inform future treatment strategies.