Good prognosis for follicular lymphoma with estrogen receptor α‐positive follicular dendritic cells

<jats:title>Abstract</jats:title> <jats:p> Follicular lymphoma (FL) has a meshwork of follicular dendritic cells (FDCs). We previously demonstrated the presence of estrogen receptor alpha (ERα) <jats:sup>+</jats:sup> CD23 <jats:sup>+</jats:sup> FDCs in grades 1‐2 FL. The significance of FDCs as a prognostic factor in FL remains unknown. The current study aimed to compare clinicopathological features, including prognosis, between FL with and without ERα <jats:sup>+</jats:sup> FDCs. This study evaluated the clinicopathological significance of ERα expression in 70 FL patients by immunostaining. The presence of <jats:italic>ERα</jats:italic> mRNA on FDCs from 5 FL patients was confirmed by CD21/ <jats:italic>ERα</jats:italic> double staining (immunohistochemistry and in situ hybridization). We defined patients with frequent ERα expression as the ERα <jats:sup>high</jats:sup> group and those with infrequent ERα expression as the ERα <jats:sup>low</jats:sup> group. Thirty‐two patients were assigned to the ERα <jats:sup>high</jats:sup> group (45.7%), and 38 patients were assigned to the ERα <jats:sup>low</jats:sup> group (54.3%). Both overall survival (OS) and progression‐free survival (PFS) were significantly better in the ERα <jats:sup>high</jats:sup> group than in the ERα <jats:sup>low</jats:sup> group (OS, log‐rank, <jats:italic>P</jats:italic> = .0465; PFS, log‐rank, <jats:italic>P</jats:italic> = .0336). Moreover, high ERα expression on FDCs was an independent prognostic factor for OS in both the univariate ([hazard ratio] HR, 0.163; <jats:italic>P</jats:italic> = .0260) and multivariate (HR, 0.050; <jats:italic>P</jats:italic> = .0188) analyses and for PFS in both the univariate (HR, 0.232; <jats:italic>P</jats:italic> = .0213) and multivariate (HR, 0.084; <jats:italic>P</jats:italic> = .0243) analyses. <jats:italic>ERα</jats:italic> mRNA expression was detected in CD21 <jats:sup>+</jats:sup> FDCs within the neoplastic follicles of FL patients. In conclusion, a neoplastic follicular microenvironment with ERα‐positive FDCs might affect the grade and presence of the follicular pattern of FL and improve patient prognosis. </jats:p>