Clinicopathological and Gene Expression Analysis of Hyaline Vascular Castleman Disease

Introduction: Hyaline-vascular type unicentric Castleman disease (HV-UCD) is a classic variant of Castleman disease, characterized by localized lymph node hyperplasia. Due to its rarity, there have been few systematic reports summarizing its clinicopathological features globally. Also, its pathogenesis remains unelucidated. The present study aims to provide a detailed clinicopathological and transcriptomic analysis of HV-UCD to enhance the understanding of its underlying mechanisms at a molecular level. Methods: We conducted a clinicopathological analysis of 51 HV-UCD cases and performed whole transcriptome analysis on frozen lymph node specimens from four cases. Differentially expressed genes (DEGs) and Gene Ontology (GO) analyses were performed to identify significant pathways and biological processes involved in HV-UCD, with reactive lymphoid hyperplasia as control. Results: The mean age of HV-UCD patients was 42.8 years, with no significant gender differences. The most common sites involved were the abdominal cavity (n = 18, 35.3%), mediastinum (n = 11, 21.6%), and retroperitoneum (n = 9, 17.6%), with an average size of the lesions being 4.8 cm. Histologically, 33.3% of cases exhibited “dysplastic follicular dendritic cells (dFDCs)” characterized by multinucleation or large nuclei within and outside follicles, positive for follicular dendritic cells (FDC) markers. DEGs analysis compared to reactive lymphoid hyperplasia revealed significant upregulation of genes related to FDCs and angiogenesis. Notably, the placental growth factor (PGF), a proangiogenic factor and a member of the VEGF family, demonstrated significant overexpression. GO analysis identified significant enrichment of genes involved in angiogenesis, cell adhesion, tissue architecture, and humoral immunity. Discussion: This large cohort of HV-UCD cohort provides potentially novel clinicopathological insights. Gene expression analysis demonstrated increased expression of FDC-related genes, suggesting a pivotal role of FDCs in HV-UCD pathogenesis. The differences in the gene profiles related to angiogenesis may contribute to the distinct mechanisms and histological features of HV-UCD and iMCD-TAFRO, where HV-UCD is associated with hyalinization of vascular walls and iMCD-TAFRO is characterized by angiogenesis with endothelial cell swelling. Conclusion: The present results suggest the crucial role of FDCs in HV-UCD pathogenesis from the molecular features. Currently, there are no objective diagnostic markers for HV-UCD. Identifying these markers may lead to a clearer understanding of the disease pathophysiology and improve diagnostic accuracy for HV-UCD. Further investigation is warranted to verify the findings.